Wearing my sisters prom dress and shoes?

Will it be okay if I wear my sisters grade 12 prom dress from last year, it is SOOOOOOO pretty, and no offence, i don't mean to be rude but I saw all the other girls prom dresses on facebook, and I think the one I'm going to wear looks 10x more beautiful and elegant.. It's light purple but it's like silk. with black sequence down the middle. It's from Be Be so no one else would have it.. I think I'm going to wear the shoes that she wore with it too? Prom is in a couple days so I can't go out and buy a new prom dress now... And I'd rather not spend money on a new dress, JUST for grade NINE prom, for grade 12, ofcourse!! but not for grade 9..Do you think people will point it out or laugh or something??? Btw, this is my grade 9 prom! :) I doubt anybody I know saw my sisters picture with her wearing it.. But tell me what you think about this? thanks