I have to agree with Morriswalters, although Mira has a clear point.  For the most part, Bonea is going to be pretty worthless as an information source.   Perhaps a few useful bits mixed in with a lot of useless junk.

But it is clear that all the immortal powers are highly constrained on how they can interact with mortals - including by providing information.  Bonea is a loophole.  Immortal knowledge without immortal constraints.  Her nature makes it almost impossible to get that information, but the possibility for success is not zero.  At some point that loophole will become critical. 

However, I would argue that, from a literary standpoint, Bonea is a lot more than a information loophole or a valid reason to provide readers with an info-dump.  Just like Maggie or Molly, Bonea is going to be one of those individuals that helps define Dresden's character more clearly as well as providing emotional (funny, heartwarming, sad, etc) moments of emotional impact. 

We learned in Skin Game that Lashiel is perfectly willing to "adjust" the perceptions of her host to get that host to act in the desired way.   We learned in Dead Beat that Lashiel was able to deceive Dresden even though he had not formally accepted the coin. 

So key question, were there instances between Dead Beat and White Night where Lashiel deliberately deceived or hid things from Dresden (using her illusion power) to keep some important information from him - or perhaps to create false information from a trusted source. 

Some possibilities:  Information that might identify "Cowl", information about necromancers/necromancy that bite him in Battle Ground, Something about the White Court?    No idea, but there do seem to be some possibility here.

Lara gains A real ally in Winter. The White Court is the weakest vampire court that we've seen.

I think it is fair to say that in a 1-1 battle, a white court vamp is weaker than a Red and definitely weaker than a Black.  The White vs Red match will be equal for a bit - until the white vamp runs out of energy and then it is killed.   The Black vs White will end quickly with a dead White.

HOWEVER, that is a long way from saying the White Court is the weakest vampire court.  Arguably they are the STRONGEST court if your focus is on the mortal world.   Which is why I think Mab wants them as allies.  The focus of the conflict is the mortal world going forward. 

If you follow the classics, then Dresden will see three major changes --- all changes that make for a very painful realization for Dresden. 

1) One close ally who is now an enemy

2) One deadly enemy who must be an ally

3) One treasured companion was dead is now alive

4) One friend who is changed for the worse

5) Someone new who he learns a great deal about --- so that he can show off in a later book


The ally that is an enemy is almost certainly Michael, but honestly that is probably too simple as a Knight of the Cross would be able to tell that this Dresden is now their Dresden.  I would argue that the ally who is now an enemy is Murphy - which also nicely ties up #3 as well.  And Murphy would be a very dangerous foe for Dresden for many reasons.   You can make the case that a Susan as Red Court vamp would make a good enemy as well, but it feels weaker. 

The enemy who may be an ally.  Again the obvious answer is Marcone, but also again that is too simple.  To really make this hurt, the ally has to be a serious enemy.   That means you are looking at Lashiel or Nickodemus - both would make very painful allies.   Other possibilities (Maeve, Lily, Merlin, Red King -- simply do not have the emotional connection to make this alliance BURN Dresden's soul. 

Treasured companion now alive is obviously Susan or Murphy - and you have already read why I think it would be Murphy. 

Friend changed for the worse is most obviously Molly, except the author has already put Dresden through a lot of heartache related to Molly.  A case can be made that Charity could be the one that turned in a dark direction if the change resulted in Michael's death, especially if Dresden is at fault.     

Somebody new is pure speculation, but I think this would be a great book to tell us a lot about the federal agency focused on the supernatural.  And the payback in later books when Dresden shows off would be golden.   

This is an interesting plot twist that can go so many ways

Pluses
1) Dresden and Lara have a great deal of respect for each other.   
2) They are also clearly attracted to each other in a way that has nothing to do with magic or inner demon beings
3) This ties Lara even more tightly to Mab -- a very strong political alliance for Mab.  After all, the White Court has a great deal of power in the mortal world - where Mab is fairly weak (relatively speaking).
4) It demonstrates Mabs power over Dresden in a very public way right after he was just super scary
5) It provides another layer of protection for Dresden vis-a-vis the white council.  I am sure there are other allies of the White court that would not hesitate to target Dresden before but would hesitate after a marriage.
6) Does this give Dresden access to white court resources?  Aka - cash and favors? 


Negatives
1) Lara feeds on souls -- so hard to see how they can have a marriage without that being a pretty strong barrier
2) Dresden is going to resent the hell out of a political marriage and that will create a lot of issues.  And if it becomes a real marriage then either Mab loses a lot of control over Harry to Lara (aka - she feeds on him scenario) or it turns to love and this becomes very damaging to Lara. 
3) A lot of worry that Lara is infected by outsiders based on odd behavior.  That could have been Justine distorting things-- or it could be a real sign that Justine infected Lara (or visa-versa as her father was probably associated with outsiders as well.
4) A distraction for Dresden. Normally that would be a good thing for Mab, but things are very ugly right now and having her winter knight be off his game would be dangerous. 
5) A political marriage involves obligations on both sides.  What would Mab promise Lara to make this happen?  Or does Lara already owe Mab too much to say no. 
6) Kids - enough said
7) Lara is the responsible type -- and a soul eating vampire.   Relations with Maggie will be complicated.....  of course, this might explain why Maggie goes to boarding school.... 
8.) Dresden will have obligations to Lara that might conflict with his obligations to Mab.  And Mab cannot just override such obligations as winter law applies. 
9) Lara's family are mostly a bunch of monsters.   Her extended family/court even more so.   That cannot end well when Dresden walks into the room.  And they are unlikely to take a few random deaths as well as the winter court did. 

He didn't try and take Justine to Demonreach and imprison her because between the battle itself and the effort required to bind Ethniu, he was running on fumes. He could barely stand, let alone throw his Will against a Walker.

This makes no sense because he was willing to confront the outsider on the boat where he had access to none of the resources of Demonreach.  If he was too weak, then he should have made up some excuse to stash Justine somewhere else.  Not confront her on the boat. 

The shield bracelet and stuff made life easier..  The island has a lot of stuff but it isn't exactly the local
magical Ace Hardware store, Harry made due with what was at hand. 

This also makes no sense.  He had a number of visits from Thomas and Murphy while on the island.  He could easily have asked Thomas to acquire a set of tools and some raw materials.    Yet he scratched his staff out with a nail or something instead.     I get that after skin game he was highly distracted and seemed reluctant to get back in the game which may be a natural human reaction, but the time between cold days and skin game is inexcusable. 

I wonder why Dresden burned Carlos during the meeting.    Yes he had to create a distraction, but why target Ramirez (aka - a friend) rather than some warden or other attendee at the meet and greet. 

Other enhancements are just as powerful.  In no particular order as I cannot remember which book provides which.
*  After training molly, he can do veils a lot more easily
*  In ghost watching molly, he sees the power of illusion
*  As winter knight, he starts to effectively use cold magic -- first in Changes with mixed fire/cold attack, but I would argue more effectively in cold days
*  Reputation is power in the supernatural world - and Harry both builds reputation and leverages his reputation to get things done
*  His resistance to outsiders realized in cold days
*  His ability to block pain learned in Dead Beat from Lasciel
*  His summoning in book 1 that he used again a bit later in book 4 or 5, but not much since
*  Necromancy knowedge gained in Dead Beat.  he does not use much, but he did use
*  the ability to understand and speak multiple langues (and access to magical theory/history) gained from Lasciel and lost when he gave up the coin
*  He picked up mind magic in a much more effective way (defensively at least) after Turn Coat
*  Bear power belt showed up in book 2 and never came back*