Anippe is a Mokolé. The Mokolé's view of vampires is as follows:
"You think [the Garou] hate those things? Imagine how we feel. The blood-devils are destroyed when they see Sun's face. ...They took Egypt away from us and destroyed it. From Kin I hear the blood-devils fight each other. Maybe they'll kill each other. That would be good."
(From Changing Breed: Mokolé, p. 45)
Given the above, she's not going to view the idea of allying with vampires favorably, no matter the reason. Thus, her reaction.