I don't LOVE "Single", however this is going to do about 10000 times better than "I Bruise Easily" would've ever done here. As some others have mentioned I think "The One That Got Away" would be MY personal choice for next single.
"Single" is more spring/summery and upbeat, I think this was a pretty good choice and will showcase her diversity as a singer. Radio LOVES her now, so this should be another surefire hit!