So sorry to hear about the increase in symptoms. If possible, I would definitely move her to weekly with her therapist. It sounds like doing more ERP around the fear of throw up would be good. Also eating sweets as an exposure might be helpful?
I would also work on how she reacts when feeling nauseous. It can help to learn how to relax the body and not fight the nausea, as that tends to make it worse. This youtube video speaks about that: https://youtu.be/N64tVmsfwYQ