Could really use a bit of advice about a girl in grade

I'm only 17 and don't have much experience with these kind of things. I usually just keep quiet about it and get on with my life but this one seems to be eating me from the inside.

There is girl called Shannon, she is a senior just like me. I have never noticed her before until this year and she apparently lives down the street from me. I find her adorable!!!

I can tell she has low self esteem and have heard people talk about how ugly she is(she has bad teeth). But i find her absolutely lovely. My teenage hormones can barely be kept in check. I just find her ADORABLE!!!!!!

I was talking to a friend in art class and she came up and asked him a question about their project and he kind of blew her off. I remember thinking in my head "shit shit shit she is coming over here, she is so adorable". She left without saying much and i kick myself everyday for not talking to her, asking about her, just ANYTHING. A couple months pass and i see her every other day in a computer class. She is always wearing her headphones and i can tell she is very lonely and doesnt have much self esteem. I hate seeing her like that, because she is so freaking beautiful despite her teeth, which i don't mind at all but my friends seem to get hung up on them. Anyways, we will be graduating soon and i just wish i wasn't too big of a pussy to say something to here. She seems content with herself but i have noticed that she is a very lonely person and when i see her in the hallway she always seems a bit depressed or mad. I know i should really just man up and say hello and make her laugh because i FUCKING ADORE HER SMILE. But i just can't, there is no good time to do that. She is always wearing her headphones and on her laptop, i don't have any classes with her and every time i see her she just doesn't seem like she wants to be bothered. I have never really seen her talk to anybody. Oh my god this is just too much, i wish i had a class with her. I keep telling myself that i will kick myself for at least not saying something before the year is over and i never see her again. But i just can't bring myself to do it because i'm a pussy and there never seems to be a proper time.

Me and my friends used to talk about "girls we would bang" but after seeing this girl, I don't want to bang anybody. I would rather have a 5 minute conversation with this girl than a whole day with Jennifer Lopez.

I JUST DONT KNOW WHAT TO DO!!!!!!