How should I go about talking to this girl?

So I live in a small town. I’m 25 and everyone from high school still hangs around. Anyways there was this girl I was never really attracted to in HS but I suddenly can’t stop thinking about. She’s the sister of one of my brother’s best friends. Me and her brother are friends, I don’t see him much but when he’s around we usually talk for a while.

I messaged this girl on Facebook a few months back for the first time in years. I just basically said “Hey, what’s up?” Just normal conversation. We didn’t talk much considering the conversation was kinda stopped. It really wasn’t her that ended the conversation abruptly, but me considering I got really nervous texting her and felt like I was bombing when in reality I was probably fine. Anyways, I just can’t stop thinking about her. Any advice for how I can get in contact with this girl without coming off like a total creep? It would help a lot. I feel like social media is a weird way to talk to people that you haven’t seen in a while without coming off like a creep.