best (female) friend moved away for a few years but moved back - i dont know how to act or feel.

My best friend who moved away around 4 years ago moved back and we're attending the same school now. Im not sure what my feelings are right now; I might really like her but I might just think that because im happy to see her. We have one class together and I see her in the library alot but im not sure how to approach her. I cant tell what she thinks but it doesnt seem like she wants to talk. She usually walks up to people and starts a conversation but whenever we have been in a line together or we're sitting next to eachother she seems like she notices me but doesnt say anything. She's always been a complete extrovert and always speaks what's on her mind but it kind of feels like she doesnt want anything to do with me, though I might be over thinking it. I feel like it might be akward now since the semester is almost over already and we only greeted eachother two times. Im a bit shy and i realize that i should have done something by now but we're almost out for break and i doubt we'll have the any of the same classes next semester so im worried i wont get the chance to talk with her. I know this seems like some elementary or middle school love story but relationships are extremely important to me and i really want to rebuild ours at the least. We were really good friends but now we barely talk to eachother. Does it seem like she is waiting for me to do something? Maybe im overthinking all of this but i really dont want to ruin any chance at being friends again or maybe even something more with her. Any advice on what i should do would be appreciated.