Give your friend props for being unoriginal and uncreative. Then let it go.

Perhaps you live in a small city where there is not much choice of venues?

Your wedding is still YOUR wedding, it will be unique.

I know how you feel, my husband's "friend" stole our wedding DATE (we wanted a NYE wedding).

Focus on making your day unique to YOU. The ballroom and time of the wedding are not what people will remember. The faster you get over this, the better for YOU.

Good luck!