Hmm from what you've told me, it doesn't really seem like you two have too much going on right now. Maybe she's hoping for more? Or maybe she's just bored about talking about school with you. She did admit fears you to though, which demonstrates vulnerability. So my advice to you is if you aren't afraid to be rejected, to not give up just yet. You could take a few routes though, definitely avoid simply saying Hi.
A. One thing I love doing is pretending to show interest in the friend, preferably a less attractive one, of the girl I'm actually after. I'm not sure if that would work in your situation though, as you two haven't seen each other of out school.
B. You could leave her a message informing her of plans you already have, and invite her to come along. Make sure these are group plans though and you want her to know that these plans are happening with or without her.
C. Ignore her entirely. If more than two weeks have passed, and she hasn't made any effort to come to you then move on with life entirely. Don't look back and don't ever get tempted to even say hey to her.I'd probably go with C. If a girl isn't already interested, there isn't much you can do. First impressions are pretty big in my books.