How can I befriend someone I've never spoken to for the whole of our high school life without coming off as a creep?

Anonymous
For a little bit of backstory, we’ve always had a lot of brief encounters during high school. We’ve greeted each other, but never bothered conversing, let alone having a deep conversation. Not because we didn’t get along, but mainly because we at least weren’t interested in getting to know each other. One day, I performed on piano in my high school, and she went to add me on Facebook and Snapchat. Despite that, we still never bothered messaging each other via social media.

I’ve snapchatted her in the past with no response. However, one day, she replied to my Snapchat (the first time she’s responded, two years after we graduated high school). From the conversation we had, I discovered she had a bit in common with me. And craziest of all, she’s a five minute walk from my house (she doesn’t know I know this haha). From that moment she replied to me, I wanted to get to know her more, and don’t want the communication between us to die away. Except, it’s difficult finding things to talk about to her, due to the fact that we’ve never really spoken to each other, meaning I don’t know anything about her, regarding what she likes and all.

My worry is that I may come off as a creep. She’ll probably be thinking why after all these years does he choose to approach me? It’s also more awkward, as were opposite genders and she doesn’t have a terribly good impression of me.

I should also add that she's got a boyfriend since last year. My question is because of the past and now having a boyfriend, would it be wise to leave it as is and not bother befriending her? Or should I try? And if I should try becoming friends, how can I do it in a way that’s natural and not creepy. Your advice will be greatly appreciated.
Updates
+1 y
Thanks for the great responses everyone!! I messaged her and got a really positive response!! Now I just have to gradually get to know her, which may be a bit difficult
How can I befriend someone I've never spoken to for the whole of our high school life without coming off as a creep?
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