We need to get Anthony Stewart HEad in here somewhere.

We're all from a bizarrely large family following the whacky capabilities of Joss Whedon, and we're obsessed?

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Morgan-- Alan Rickman    You need menace.  the problem is that before Turn Coat Morgan has few dimensions.
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Nicodemus -- Christoph Waltz--- have you seen inglorious basterds?   
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Well sort of a joke. 

Here is where it all came from:
JB has written that we all have missed two major clue bats in turn coat, and quite a few of us went gonzo trying to figure out what they are. I Believe it was He Whom Walks who first noted that in turn coat, when Harry is searching for Thomas, he does not use his most obvious tool, little Chicago. In fact, it’s not even mentioned in the book at all, unlike every other book when it is used or not, only referred too as a ‘tarp covered table.’
Second, Harry has nasty headaches throughout the entire book. Now there are several ideas about these headaches, many of them involving his brain damage, but especially in light of his not having them in changes, it seems clear these headaches are cause by someone messing with his head, just like the headaches he got in small favor when Mab messed with his head… hmmm…
Third, someone has messed with little Chicago before, during proven guilty, when Mab was involved oh so strangely with Molly. (more on that later.)
So, this led some of to speculate Mab had messed with Little Chicago again, or at least made Harry and Bob forget it existed at all. But Why?
Removing Little Chicago prevents Harry from finding Shaggy and Thomas directly. It has several results, but the largest is it forces Harry to bond with Demonreach, something that JB has written he ‘will deeply regret later.’ Note that Mab, at this point, has considerable other options; She could, for example, have just walked in and offered Harry the winter knight job in return for her help rescuing Thomas. Or unleashed Lea. And those are just the unsubtle options.
Ergo, if we follow this logic, Demonreach is important to Mab, and it is important to her that Harry have it. Why? Well, many possibilities, but in my scenario, it is because Demonreach is the earthly location of the sidhe table (it is directly below it, remember summer knight); this is where, 75,000 years ago, a mortal wizard ascended to become Mab, causing the last major ice age. ( And creating that lovely source of permanent dark magic the island’s warden protects.)
It all came together one night when I was really tired and remembered JB had said this:
‘Well its one of the Laws (time travel) and Harry hasn’t broken it yet, so he will have too.’
So we have Mab, who knows way too much about what is going on and what will happen in the future, who can walk right thru all of Harry’s wards anytime she wants, who forced Harry into the position of Demonreach, somehow predicting that he would take that option…
We have Lea, quite interested in Molly, even back when she was a kid.
We have the entire darn book of Proven Guilty.
We have Molly, whom has powers of illusion, enchantment, and mind control.
We have Mab, whom was probably human once, quite legendary for her illusions, enchantments, and mind controls.
And we have Margaret Katherine Amanda Carpenter; Margaret from Marvarid, also spelled Margot, Marit, and Maeb..or as JB spells it, Mab.
Time travel + location of sidhe table + eternal regret of Harry … Molly is Mab.
As to the rest of the queens, I suspect they came later actually, (Mab says she IS Sidhe, not she IS A sidhe.)…Molly recruited them to balance her out, and end the ice age she accidentally started.
Or as others have suggested, her personality split into pieces..but im in favor of the recruiting idea.

Enjoy disproving.