Undercover and Save The Day would flop. They are too boring/similar to Slow Down. I love LWR and a ballad following two dance hits could be good, but it's not really single material. Birthday would be a good choice but it's already confirmed that it isn't going to be a single anyway
Write Your Name & Stars Dance are risks but maybe they could do well...it might be a chance she has to take.
Like a Champion and Forget Forever aren't single material/would flop so they're out...
So, I think either Write Your Name or Stars Dance. It may be a risk but if they do well it'll be best for the album. I want Birthday most but she said it was going to be a single (meaning they changed their mind)