Yeah I know. I actually made a date with one I've been after for a while last night, which made me forget about the other one. Still no one likes being rejected, although we know that there's no way every single girl we're interested in is going to feel the same way.
I think my age is finally catching up to me. Most of them think I'm mid 30's (this one did too), and when they find out my real age, I can sense a difference.
Anyway, as to your situation, I can sympathize. I wasn't totally sure about mine either. She stayed over last Saturday and the evening went well, but she just wanted to hang out. I'm all for being friends with women, but it DOES complicate things.
So when she's over, try some light touching. Nothing sexual, just touch her shoulder, back, hair - not in a creepy way - just see what the reaction is. Pay close attention to her eyes. If the pupils get big when she's talking to you or vice versa (you should be looking directly into here eyes when you speak to her if possible), and she touched her hair a lot - she's interested.