I like this girl but I don't know if she's interested?

I used to be part of a local community radio and first came across this girl at one of the social evenings. She was the daughter of one of the members and is passionate herself about pursuing a career in radio.

We didn't really interact much at the event but we were both at a local fair several months later that the radio station was broadcasting from. Interestingly, at one point, she came up to me and started keenly talking to me and we just ended up chatting for those next few minutes. We ended up going on one of the fast rides together and hanging out a bit after as well before she went home with her parents.

That was over a couple of years ago now and I haven't seen her or really spoken to her since. Annoyingly though, it sounds like we have a lot in common. I heard from someone at the station that she has Asperger's (which I do also) and we seem to have a lot of similar interests as well. I feel like she's definitely someone I'd like to get to know more.

I don't really know what to do though. End of last year, she put a long post on her wall saying what a difficult year she'd had (some of the things she talked about were pretty terrible) and I sent her a message in response, just telling her how strong she was, what a great person she is and that I was always there if she needed to talk about anything. She opened it but never responded and I just don't know what to make of that.

She lives in London at the moment and is a student at the Global Radio Academy, so it makes potentially meeting up a little awkward. But the other week I was in a local Lago Lounge and I swear I saw her there as a waitress (she has done waitressing in the past) and she kept looking at me, almost as if she recognised me, but we didn't say anything. I wasn't 100% sure whether it was actually her or just a fantastic lookalike so I didn't try to speak to her just in case.

But the upshot is, I feel like I'd like to try and get to know her better and this would inevitably be best achieved through messaging. What could I say? And is this a good idea given how much time has passed? (Or am I massively overthinking?) Thanks for any advice!