You already know what to do. if you don't, do this: think how you'll feel about wearing it in the midst of a group of 20-year-olds. Will you feel comfortable doing that? if you cannot honestly say yes, don't get it. it's never about what others think, it's all about how YOU feel in it. I have a short cropped jacket and it looks great at home but if I'm not feeling good about it I don't wear it because honestly, that's something you more often see teenagers wear.

I don't think this is about age, but more about style. I think it is a lovely dress, but I know I wouldn't feel comfortable wearing it because it is too girly for my style. But I have friends the same age who would wear it and look and feel wonderful. Is this dress congruent with the things you already have? If so, go for it! If not, maybe consider if you will feel fab or self-conscious when you wear it.