prom dress

i am so in love with this prom dress it's insane. i am very self conscious and get bullied a lot at school ( ex. when i wear white shorts people will put pen all over my seat and chocolate so when i sit down it's gets all over me) people suck. anyways i really just want to feel like a princess for one night. my mom knows how unhappy i am and how much i get picked on in school but she can't afford a $500 dress and $200-$300 alterations because of my height. i have a lot of money from my job but i want to save my money for college. i'm torn between if i should by this dress or not. it makes me feel so confident and beautiful but that is a lot of money for one night.

what are your peoples thoughts on this dress/prom?