How do I stop this annoying girl from bothering me?

Okay, so I am a 10th grader. Last year there was this girl in one of my cles. Like we weren't friends or anything. I've worked on 2 projects with her but rarely ever talked about anything personal. Basically, I dont consider her to be a friend or anything. Like idk hoow but one time last year she looked me up online on some site and found a few nicknames I have that I wrote on it. and I was wondering why she looked me up in google in the first place.. I still dont have that answer. So she was like thinking it was embaring and stuff when she said it during cl, probably,.. when it wasn't. her and some of her friends in the cl were kinda like her too.. like one girl was just a follower of what the 2 other girls said, while the other like it was more obvious that she was trying to be mean by 'putting others below herself'. so yeah i havent talked to that first girl since last year and then all of a sudden this year she keeps randomly saying hey to me in the hallways. usually when shes around her friends. like i have volleyball after school and she has cheerleading so its usually then and she like says "Hi/hey [mynamehere]!" and its like totally unexpected. she says it with such enthusiasm and then the people shes with onlook semi-smiling and anticipating my reaction.. but idk how to react! and since when someone is saying hey to me i check who says it, i see its her and am like wtf cause im not friends with her or anything.. and people usually say hey to people they are remotely friends with. i think shes doing it as a joke or something. like it catches me off guard so i just act like it didnt happen and ignore it. like today i was in the middle of cl taking a quiz and she like does it again in the hallway too when she was in a diff cl. like idk what to do. like i cant just ignore it.. like if she truly wants to be my friend which shes currently failing at then i dont get why she'd do that. but im assuming shes just trying to make fun of me or something so how can i put an end to this? i dont want to have friends who do stupid sh** like this anyways. i like when people are straightforward. like i was going to send her a message on facebook but idk what to say or anything.. or should i say something IRL instead? please help me guyssss. thanks.