Sudden Contact???

This is not about a current friend, but someone who I WAS friends with years ago. Like, nearly a decade ago. We stopped talking sometime in high school, I don't even remember why except there was some sort of falling out in our friend group. I don't remember very much about this person but we stayed Facebook friends all this time and she occasionally will like or comment on my stuff. At one time she was my best friend but as it stands now I know nothing about her and I'm not particularly interested either. I'm a different person now and I'm sure she is too. However she randomly reached out today after almost a decade of not chatting with me privately and now she wants to grab lunch and talk? I feel like somethings weird about that even though it seems like it could just be an innocent desire to catch up. Plus I have a ton of anxiety about it because I don't know anything about her and remember her being kind of odd (and not in the fun way). I know she remembers more than I do otherwise she wouldn't have reached out. I agreed anyway because who knows, it could be pleasant to meet her again. But has this ever happened to anyone else? How should I handle this?