Should I be worried that she didn't message me back?

[Shelly]

Ok, like guys, girls also need their space. Girls are complicated in the way that they can be really in to some one one minute, and then want to have anything to do with them the next, (I think it's just part of our hormone processes). If I were you I would just keep a bit of distance from her for little while, let her come to you, trust me, us girls love moments of intense interaction and then we need a break for a while. If she's in to you (and it sounds like she does) she'll text you back soon, or talk to you soon, but for now just keep it low key, and relaxed - it's a way of showing that you understand and respect her space