<human>: Let me start with I am unsure of her age right now. Guessing 16.

Maybe this more so a post looking for advice than a problem? There's this girl I find really pretty. I see her around the school often. A few months ago I introduced myself and started talking to her. After the small conversation she had to leave and that was it. I see her around my school but only from afar. Whenever I go to talk to her nowadays I get really nervous (she's very pretty) and just end up passing by her and maybe giving her a smile if she see's me instead if going over and talking to her. I wanna get to know her though. 

I am having hard time telling if she's even a little bit into me. Whenever I see her she seems to tense up (kinda like get shy). For example, this morning I was walking in the campus looking at reddits front page and noticed her in my peripheral vision. She clearly noticed me as she was going in a door and kinda tensed up (shy'd up maybe? I am having a hard time describing it.) and went in like she was in a hurry. I can't tell if she's trying avoid me or if it's something else.

Any advice on what I should do? I'd like to talk to her more and eventually ask her on a date but I don't wanna make her uncomfortable and or take any signs wrong. Maybe I am over thinking this.

Can you provide a brief rundown of the text in within 3 sentences?
<bot>: I want to take a girl on a date, not sure if she's into me at all, don't know how to approach and find out.