prom with a girl

Blaire

Ok so I need some help......im a female and my female best friend just asked me to prom bc her bf can't make it, she's wearing a dark blue ball gown, so what should I wear? should I match her and wear a dark blue mermaid dress? or should I have a totally different color dress? like red or purple? and should it be a long dress or a short dress? if I were a guy I wouldn't have an issue with this but I'm confused I don't want to ruin her dau