<human>: EDIT: I don't know how flairs work, please don't shoot me!

Okay r/Relationships, here's the thing. I'm [16M] a junior in high school and the captain of the Front ensemble in our Indoor Drumline. Yesterday, my friend [15F], a sophmore we're going to call Alice, asked if I was going to junior prom. I reply that I might, to which Alice jokingly asks if I needed a date. Being the person I am, I tell her that if she's offering to be my date, I'd take it.

She does something I don't expect, Alice says that she is willing to go. She has a boyfriend [15M] we're going to call Greg, and he's one of my best friends. I've always had a thing for Alice, but I'm about as confident as a potato so when she broke up with her first boyfriend I never got the chance to move in.

Greg is fine with the whole idea, thinking it's a friendly gesture, but it makes me worried. He's never been one to take something like Alice suddenly deciding that she wants to be with someone else, and if that happened at Prom, he'd find out after the fact and it'd be a bad time for everyone.

How can I tell Alice that I like her, without ruining my relationship with her, Greg, and her friends? I'm about as good with relationships as I am with math. I failed math 4 years in a row.

Can you give me the gist of the text in a nutshell?
<bot>: What should I do if the girl I like already has a boyfriend and she asked me to take her to Junior Prom as a friendly gesture?