>She's been busy with school starting this week and working before school starts.

This is your answer. If you know she is busy, it's natural for her not to get back to you. If you hound her with messages, then you're going to give off the wrong impression. In my opinion, you should wait a month even if you don't want to. If after a month and she doesn't get back to you, then you should try a more aggressive approach.