A.Z.
She could be teething or suffering from and ear infection. Keep offering the breast, it should pass if it's something simple.
If it's something you are eating that is causing a reaction, she may wean or she could have decided the bottle is due to less work, but typically it's not such a drastic change. So I think it's a pain reaction the way you described her behavior. But I would take a good feel in her mouth and see if there is any swelling on the rom teeth coming in.