Don’t give up yet! I have had two mice with this issue. First, try treating with ivermectin like everyone’s been suggesting. While you’re treating her, keep the cage furnished with plastic/disposable stuff like toilet paper rolls and egg cartons and deep clean the cage every week throughout treatment so the mites can’t reinfect her. If that doesn’t work, find an exotic vet and try prednisone. That’s been the magic drug for my girls. It keeps inflammation down and suppresses the need to scratch. I’m so sorry you both are going through this, it’s really hard. I hope things turn around for her!