No idea if she will win a slam, but I think she can obviously. The age thing is a factor but she started playing later than most girls so that's why it's that way. It definitely shortens her window.
I figure if she was somewhat close to beating Justine and making the final last year, that may indicate good things for the future, but there's still things she needs to put work into imo before she wins one. That's the big question.