Girl advice - What should I do about this?

I need some advice on what I should do really. Sorry its going to be quite an exhausting read:

Basically, there is this girl that used to be in some classes at school, and have known of each other since year 6. I've always liked her and i've always seen something different in her compared with other girls. Although I was extremely quiet at school, kept myself to myself. She always talked to me and even if we passed each other in the corridor to get to the next lesson at school she always said Hi or smiled at me and I smiled back. My 2 best mates at the time also liked her too, although one of them is currently engaged to someone else and the other one, whilst single and still likes her, keeps telling me he is letting me pull her as he feels he doesn't have as much in common.

Several years down the line and we lost contact with each other. I joined Facebook about just over a year ago, and up until a few weeks ago, I decided to add her as a friend anyway, and within 2 seconds she had accepted the request. We are both the same age, 22, and a couple of weeks back she turned up at one of the town pubs with some of her girl friends and I was already there.

We got talking, conversation flowing, her best friend put a picture up of this girl and I sitting next to and cuddling each other. We discovered we had so much in common. Both have the same type of music taste which actually isn't what most people our age listen to, and our future ambitions are the same as well such as wanting a family down the line etc...

We were messaging each other in the meantime, and it seemed to be going alright, I did leave a bit of an open question like wanting to meet up again and she never responded to that.

We re-met out again down the same pub precisely 2 weeks later with the same group of friends and again conversation was flowing very well. I decided to just ask her casually whether she was currently seeing anyone and she said "Well, kind of, but its a bit complicated at the moment" Being polite and gentle about it I didn't mention it any more. Yet according to her best friend (admittedly she had a couple of wines), I asked her the same thing about the girl and she said "yes, she is single". Also it shows as single on her Facebook page as well.

We moved on to a club afterwards, she is a regular there but that was my first time in there, basically because of my taste in music I didn't belong but I gave it a go. I quite enjoyed it and it was time to go. I asked if she would be willing for me to have her phone number and she wouldn't give it to me because of her current "complicated relationship with someone else", we gave each other a peck on each cheek and called it a night.

In short, I really, really like her. Unlike a lot of girls she is naturally pretty and although she isn't the slimmest I have ever seen, she doesn't need to lose weight, I like her the way she is. I know her friends know really like her, and I think that she really likes me too.

What I want to ask is, why do you think her friends say shes single, on her facebook profile is single, yet she says she is kind of with someone at the moment and I also heard her say that to one of her other friends as well later on the evening?

Let me know what you think and I'll reward points for the most helpful answer and apologies again for what seems like my life story above!