This doesn't really qualify as a yandere yet. At this point, she just has a rather reasonable grudge against her own people for being dicks to her all this time. What distinguishes a yandere is the violence and brutality they reveal being directed even at the object of their desires, in this case Peter. Considering how the other girls have treated him so far, her final descent towards yandere status does seem fairly likely. However, there are several other character archetypes she could still land on instead.