I washed it on the delicate cycle and hung it up to dry. I pulled at the bottom while it was wet just incase it was going to shrink at all. Although I think it would have been perfectly okay not doing that
I don't know if this will help, but I'm 5'2" and about 110 lbs...I got the XS and it fits great. It's a flowy dress so there is room around the hips and waist (I think at least) cause it's not meant to be totally form fitting.