A lot can change in a few months. I don't think she would do Breakaway because
1 Before cutoff for last years Grammys (I think...) so it wouldn't be nominated.
2 It is kinda out dated by more then a year so...
3 If she wanted to show off her vocal talent BOY would be best. Walk Away would be her next single, but for a classy event like the Grammys BOY would be the better choice.

SUBG and BTHE are great, but for the Grammys?
I'm not a big fan of medleys, but nothing but Breakaway really fits with BOY and Breakaway probably won't get picked.
So BOY...