Alex, really hon, you need to talk to these girls/girl.
Thing is, when your crushing on someone, all these little looks and glances mean something. But if your not crushing on someone they don't even make your radar.

If this is the same girl from your other post, just say hi as you pass by.

If she is saying to her friend that she doesn't know why your looking at her, then she probably isn't thinking what your thinking.

That doesn't mean you can't say hi.
However stop hovering close enough to eaves drop on her conversations....this is not cool.

Good luck.