Vahl has become a member of the Circle and became a werewolf.
She also is married to Farkas, who is also a werewolf. Vahl's lycanthropic abilities are the only ones out of all her racial powers that she was not born with.
Vahl was born with Time Lord blood mixing with her Dragon blood, possibly due to distant Gallifreyan ancestry, so she has similar abilities to those of a Time Lord, such as summoning and piloting a TARDIS, creating and using a sonic screwdriver, and of course regeneration. Although Vahl has never been seen to regenerate on screen, the change in her appearance between episodes 7 and 8, and the photograph of a very ugly Dunmer which is allegedly Vahl shown in the latter episode indicates that Vahl underwent at least 2 regenerations during the long interval between episode 7 and episode 8. It is also possible that the Dunmer dubbed by Venturian as Ugly Vahl first seen in episode 141 is a future incarnation of Vahl.