awkward age gap, someone please help!?

[Ninja]

I really like this girl, i'm 17 and she's 15. I've never spoken to her and she doesn't have the slightest clue that i'm interested, i plan to change that and i want to get to know her better and, if things go well, maybe make her my girlfriend. But i know that's a long way off yet. Here's the problem, i'm soon to be 18, if i do get the ball rolling and we start seeing each other a lot more, she'll still be 15 for a few months before she turns 16. It all just seems a bit weird in my head, i don't want to weird her out or scare her off by the fact that i'm technically an adult (in the uk) and she's still only 15. like i said it will only be for a few months and i know the age gap will decrease in importance as we get older, i've been waiting years for a reason to talk to her but nothing's came up, i've finally found the courage to say hello and i want to do it now while i still can, i'll have to do it through a private message on twitter or facebook as i don't have her number. She knows who i am, she's my sister's friend so she knows i'm not just some creep. I don't want to wait until she's 16, it might be easier that way but i've been waiting around too long for her, and she's just so dam beautiful it's only a matter of time before some other guy comes along. So what do you think? will this age gap be a problem? I've finally found some courage but it's bad timing, i don't want to ruin it by creeping her out. Someone please help i really really like her.