@Alouette, Arin will fit well in this company. That said, I'm going to go over what I understand to be your strengths/weaknesses and generally just pick out anything that seems a wrinkle across otherwise smooth silk.

Arin's strengths include: Her Poison Blood, Sharp Intellect, and her Upper Class Charms. For weaknesses her Immune System is Weak and her Intellect causes her to manipulate all, indiscriminately. Otherwise, she's a woman from a rich background cast out of Lémuria for her disease and reactions to it who has now taken to metal, prosthetic limbs that feed off her poisoned blood -- how or how often, we are not told. We could assume she's picked a bit up off the apothecary she stayed with and she has a touch of experience killing, albeit on accident. This is largely a woman who was prettied and pampered until taking ill. She's tasted blood, and was briefly fascinated, but we don't know much more beyond that reaction. Maybe she likes killing or finds complex schemes the stuff of games, maybe that's what brought her here. 

I don't have much for this one except for two suggestions: Upper Class Charms seems a shoddy way of describing your last strength, but ultimately, besides the ability to read and write this what came to mind. That said, perhaps its the use of those charms and skills that highlights her Intellect? In other words, I would accept if those Charms are but a tool of her Sharp Intellect and not a standalone strength. Every character can be assumed to have more than 3 skills, but these are the most honed and apparent in their works. Given an open slot, I'd suggest a skill less commonplace and more combat oriented considering your character is as you said, 100% Non-Physical. Arin is from Lémuria, for example, you could've dared to suggest she has a basic understanding of Clockwork engineering with that mind of hers, using it to maintain her limbs and perhaps a Lémurian wheel-lock pistol. This would highlight the Logos features involved in her prosthetics as well as the bit that sucks energy from her inspired blood. Otherwise, simply being a strong archer (granted this requires a good bit of strength) would give her some means to protect herself. The second suggestion is simpler. With Krax her character is rather young, and therefore also rather new to the Night Kiss. Your character is in her mid to late twenties (I'm hoping later, as too many RPs are full of 20 somethings), has more or less been without a home a while now, but has only joined Night Kiss less than a year ago. Have you considered giving her a few more years experience with them? Seems to me it would fit well enough with her background.