Definitely not too short! You see fashion plates where dresses look almost tea length in this period, so yours is perfectly in the range of acceptable lengths. Also, ball dresses should be short for dancing...it's kind of a 'reenactorism' to see girls swanning about at balls with floor-length skirts and long trains. If it still bugs you after you have a chance to wear it with fab accessories, great hair, etc, then by all means fix it because the most important thing is for YOU to be happy...but in terms of a period look, you're doing great.