She needs to take a break from performing there, she has been performing for the past 5 years. Smart decision. Even if she went there, she would've performed SIO because it's the nominated song.
I don't think that the preparations of her tour is the reason why she's not performing. I mean Katy is in the middle of the tour, having played the SB and still performing..maybe they didn't invite her...
This doesn't make sense to me. Her tour doesn't start for 3 months so why would that affect whether or not she can perform? Has she even started rehearsals yet? She performed at the 2013 Grammys while she was getting ready to go on tour so why not this year? Plus its not like she was gonna be busy if she will be attending + presenting.
As for the alleged AMA feud, Ariana, Jessie J, and Mary J. Blige are all performing/performed at both so I don't see why Taylor wouldn't.