You're right, there's no guarantee. Still, the story and the information available leads us and Alexandra to believe that, if she's succeeded, Nemesis/Gift's new target is the Generous Ones. They seem pretty adept at weird and bone-y magic, so maybe it won't be more than a nuisance... I just don't like thinking Alex has caused trouble for someone who did so much for her.

Also, is there really any doubt JM created the nemesis?