I moved away from here roughly 5 years ago and we haven't really spoken since. We've spoken a couple of times and exchanged numbers whenever we changed them, but it didn't really go further than that.

When I was living next to her she was quite cold, bitchy, but interesting. Now, out of the blue shes texting me asking if I want to meet up sometime, asking what I'm doing now and asking whether I'm single or not. When I told her she wasn't single she texted back saying shes been with someone for just over a month now.

She then asked why I was single and I said "Because its fun, i can do whatever I want with whoever " she responded "Ah, well, you can do that when you're in a relationship too"

Whats going on? We didn't speak for almost 3 years, and then suddenly out of the blue shes texting me and giving me IOI's?

Oh, we also went out together some 7 years ago for all of 2 weeks.

I guess she has either
a) Randomly been thinking about you
b) You have friends in common or something and someone said something about you
c) She has always liked you but you didn’t see it....

I would guess B and then she realised C, because from what you have said she is certainly giving you a few ioi's
1) Randomly texting you
2) Asking if you were single
3) Effectively saying although she is in a relationship she can still have sex with you,

All you know have to do is sort out a time & date to meet