Oh wear it, please! I would have at your age, but now, 7 years older and no longer a size 8 to 10 I can't. 
And wear it with tights and heels, not bloody leggings! :o
I hope to goodness you never feel as I do now, but if you do, I promise you that you will NEVER look back and think, "If only I'd have worn a longer dress...". :)
Have a lovely time at the party, enjoy the compliments and come back and tell us all about it. :)