I dont know if itd help, but Have you tried pulling her into your chest when she bites to let go? Is really hard because the first instinct is to pull her away, but I've heard this helps. You basically pull her in, and it blocks her nose so she lets go. It can also deter her more because there's a consequence she can understand iykwim. I hope you can figure something out soon, not a nice way to end a bfing relationship