Taylor lost this one. Her Twitter post still does not excuse her Grammy speech, where it was mainly about Kanye claiming he's the one who made her famous. In the phone call she was clearly for it. She should just take her L and keep it moving.
But if Kanye went behind her back and added the bitch line (I'm not saying he did this, I don't know yet) then wouldn't she have every right to get back at him by going back on what she said?