I've never hated anyone.. until now.?

Alright so let me explain. I always like everyone, i'm never a jealous girlfriend but this one girl is always flirting with my boyfriend! it drives me nuts, and i know that is jealousy but i'm only mad because she had with my really good friends boyfriend, and also slept with some guy at her school and the next day he broke up with his girlfriend. Anyways so shes going to prom and prom i've always dreamed of getting dollied up and my prom is going to be AT LEAST 300 easily so.. she will be sitting at the same table with me and all of his friends too, this table seats 12 people and my 2 best friends are going to be sitting with me. The problem is is that I litterally can't look at her without being in a bad mood. But i don't want to be selfish and ruin my boyfriends time also.. so i know its a really hard topic and i just don't know what to do..please help.