And another thing...Justine

[Mira]

It's not the sex itself that helps the condition, it's the feeding.  Sex is just bait and the channel the Raiths like to use to get the energy.  They can feed in other ways, like Skavis and Malvora do.  (IIRC, JB once said that in theory a WV could feed on the warm and fuzzy feeling from petting a kitten, though he added that the WV would probably sparkle if they did it, so he might have been joking about that).

The White Vampires feed on emotional energy, which is also life energy.  Justine in her manic state generates too much positive energy, in the depressed state too much negative.  The emotions are the energy and vice versa.  When Thomas feeds on Justine, it takes away those excess energies, leaving her more or less 'normal'...as long as he doesn't take too much or too often, of course.  In that respect, a manic depressive is the perfect prey for a WV with enough self control to limit their take, because they can be fed on without hurting them, and even to their benefit.

(Ignoring the potential issue of supersex addiction, of course.)

And yeah, once Thomas couldn't feed on her any more, one would expect that she would either revert over time to her manic/depressive state, or have to use medication to control it.  Which might be where Nemesis got its hooks in.

Do we know for sure that Justine's illness was manic depression? As we know there are more than one type of mental illness.  If Justine suffered from a form of schizophrenia for example, hallucinations possibly could be the perfect avenue for Nemesis to enter. Can you imagine if Justine was hearing voices for example how easy it would be for Nemesis to become one of those voices?

[g33k]

Do we know for sure that Justine's illness was manic depression? As we know there are more than one type of mental illness.  If Justine suffered from a form of schizophrenia for example, hallucinations possibly could be the perfect avenue for Nemesis to enter. Can you imagine if Justine was hearing voices for example how easy it would be for Nemesis to become one of those voices? 

I don't think we know the form(s) of Justine's mental illness, no (noting that multiple-diagnoses are very much a thing).  It's not clear to me that Jim does, himself.

I doubt Jim will specifically write it as "hallucinations" though -- that really muddies the whole "free will" issue, which is thematically-important to the Dresdenverse.