1/2 frenchie 1/2 boston bit 3 other dogs with agression

My friend has a half french bulldog half boston terrier and she has always been a handful but figured that was the puppy and last time i dog sat for her, she was calm and like to sit on my lap. But this time she bit 2 dogs that were here and one is the other dog she lives with. Also found out she bit a boxer who was a guest in her house at Christmas,
They dont want to give up on her but dont know what to do? Any advice would be greatly appreciated.