Should I ask her out or let her go?

hey guys, there's a girl I really like but I'm so shy but to tell u the truth if I do ask her out I want it to be really nice and sweet so she at least realises how much I care about her that I am willing to look a complete dork :).. so I've known her a little while now we just broke up for summer holidays and were hooking up to get together with other friends and muck about at park or Sumthin.Basically just before holidays I was so ready to ask her out we were constantly talking and flirting . Sigh* (:L) but as always there's a ******* catch (ain't that a *****) which is that my friend started tlkn and seein mor of her, he was seein someone else at the time so I thought nothin of it... Then this girl stops seeing him and now they talk loads more and it's reli gettin me down so I dunno whether to go for it or see how things pan out with my pal and her :( and tbh with u guys I really have no clue what to say to ask her out lol ( I'm 15 and we share loads in common) also recently they went to the cinema without me but still not alonenow honestly, she normally doesn't go for a guy like him he has not as much in common :/ also we hung out recently and me and her wer hugging sunbathing on top of each other flirting and normally I'm shy, she's so perfect what he'll do I do to stand out, how do I make her like me THanKS ALL