Quinces Help On Clothes AH!!!!!!!!!!!!!

Ok here`s my problem, i was invited to a Quince it`s tomorrow saturday, i have a dress but my mom figures it`s too short. I think length doesn`t really matter does it? of course as long as it isn`t all hoochie length. The dress is just a little over my knee.

I need help do i need to find a new dress that`s long or just stick to the appropiate short lengthed one?

My mom doesn`t have exprienced and is basing what she`s saying on what she thinks.