My daughter keeps being bit at Daycare, What to do?

My daughter is 2 1/2, she keeps being bit by the same girl at daycare. This little girl does not bite anyone else. I have spoken to the childs mother (since we are good friends) and have tried to resolve the issue. But this has been going on for a few months now. She currently has 6 bite marks on her back and I am furious! The babysitter has tried several approaches to try to end the biting but nothing has worked. Should I remove her from daycare or wait to see how it goes? My child and the biter have been in daycare with eachother for over 2 years, when their daycare closed we ended up putting them in the same home daycare so they would already have a "friend". I dont know if I should just wait and see how things go and hope they get better or just to end the daycare relationship. Please help!