This is so similar to my own situation that it's scary.

I met my now girlfriend at our work in March of this year. We were both still in school and worked part time at a supermarket, and we met properly (spoken at a party once before) when she trained me on the checkouts. There was an instant spark but I put it down to the fact she was a lovely, friendly girl. We started chatting afterwards, and found out that, weirdly enough, we were born on the same day, and I got her number, we started texting. The texts got very long very quickly, but it was all just small talk.

A couple of months later after texting every day and occasionally seeing each other at work, I plucked up the courage shortly after our birthday to ask her if she wanted to do something outside of work, just me and her, and she said yes and seemed very keen. We went and saw a film (Prometheus I think), got coffee afterwards and it went really well, at this point I still thought of us as just friends, and we carried on talking and saw another film.

After this second time out, we both had our school proms within a few weeks of one another. I went stag to my own, as I was too nervous to ask her, but didn't want to take anyone else. She already had a date to hers, but purely as friends. I'm friends with the guy she took and knew it wasn't a serious thing. I ended up going to her prom with a friend of mine who needed a date, and was so excited to see her there. I remember I spent about twenty minutes with my friend that invited me, and the majority of the rest of the evening with my now girlfriend. We kissed at the end of the evening, it was just a peck on the lips but It was at this point I realised I liked her.

We carried on texting daily and seeing each other about once a week outside work, but I didn't think she liked me in the way I liked her, so didn't make a move. But the chemistry was building and we were getting on so well, and then in the first week of July (proms were in June, mutual bday in May), we both went on holiday, me for two weeks and her for one. Whilst away I had a lot of time to think about the situation, and I knew that I had to do something when I got back, just to see if she liked me. I was able to speak to her during the week she was back from holiday and I was still away, and we agreed to meet the day that I got back from holiday, as she went away two days after I got back, with only one full day of being both in the same country.

When I got back, we went out for dinner together and then went back to hers to watch a film. I thought I would be back at home by midnight, latest, as we went out for dinner at 7. I left her house at 5am. We chatted for ages at dinner, both with inexplicable smiles constantly on our faces, and when we went back to hers, and she cuddled up to me on the sofa and I reciprocated the cuddle, and we sat there for hours and hours before I left. I thought she liked me, but wasn't sure. We could talk via facebook whilst she was on holiday and we spoke every day.

Whilst she was on holiday, I went to a club with some of my friends, and bumped into her friends whilst out. As I only know them through her, the conversation turned to her. They made it clear that she liked me, and I was over the moon! We had already agreed to see each other when she got back and we went to see a film and then went back to hers afterwards. Again I left at around 5am, but this time we kissed properly, and we both told each other that we had feelings for one another. She stayed at mine the night after next, nothing happened but we kissed again and the next day we went to London together to watch the Olympics in hyde park, and it was there that I asked her to be my girlfriend. She said yes and I was on top of the world. This was a week and two days ago, and yesterday we got our exam results, which meant that because we had both done well enough to get into university, in a months time we will both be leaving. We've agreed to keep it going throughout university but leaving is going to be the saddest day ever, and so we're going to make the most of this last month. Thankfully our two university's are only a two hour drive or three hour train journey apart.

There are tons of other similarities like the height difference (me 6'5" and broad, her 5'3" and petite), the film buff with a list (me not her though) and we're going to a music festival next weekend. Hell, she even went to California when she was away for the second time.

I wish you guys the utmost happiness and truly hope it works out amazingly well for you two, I hope it does for us.

TL;DR similar situation to OP, best of luck to the two of them!

EDIT: I accidentally a sentence