Feeling really low today, can someone help me?

Honestly, I can very much understand where you're coming from, but i don't think that you should feel bad. Who knows? maybe she was just trying to get to know him better as a person or just trying to make a new friend. You can't ume everything. Start talking to her more and get closer to her and just see how things go. But always keep in mind that she currently is in a relationship, so don't go tooo far.