Confirmed that she could both change into her werewolf form and still compel a sim for a drink.
https://i.ibb.co/p10sc11/06-22-22-7-43-55-PM.png
Food did nothing to raise thirst, but she did get a positive moodlet from having a tasty meal. Still curious to see if she can gain vampire levels, because I no longer have access to that since the UI glitched into werewolf mode. I think the game recognized her as a vampire at first, but for whatever reason, the second transformation switched her over to being recognized as a werewolf. I haven't actually tried putting her in the sun. Done for the night with her though... Just wanted to share how awesome this sim is!!