I've been wondering this for a while now. While I'm not blind to what looks good and what doesn't, I can't seem to figure out how to dress to look a bit more "grown" as my body naturally makes me look younger. I don't want to wear revealing clothing, that's not what I mean by grown, I just want to look more my age. My body is SORT OF like a rectangle, I say this because while I do have curves in the waist area (I'm not completely straight down), my hips are very narrow (I guess this could make me look more like an inverted triangle). Not only that, I'm 21, only 5'4" and 125 pounds, I'm naturally petite, it's not something I can change. I have noticed that things belted around the waist look good on me (especially dresses). As far as everything else, I just kind of have to say that looks pretty (or it might on someone else) and wing it. I've wanted to go shopping for fall/winter clothing for the past few weeks, but I've been avoiding it because I get upset when nothing in the store fits me right. I almost wish I had my own personal tailor or fashion adviser. Maybe it's all in my head, I don't know. I'm just getting sick of being out with my husband and family and being introduced to someone for them to look at me crazy when I tell them I'm 21 years old... even worse when I get the occasional "Well, you look like you're no older than 15". It's embarrassing.
I don't know if it's your body or your style. You might want to look at the ladies clothes in department stores for some more mature looks. I have always looked really young too, I was asked if I was old enough to be working week day mornings when I was 23, so don't worry about it. Wear whatever you like and let other people deal with it. It's you that needs to feel good in your clothes not them.
It's all right to call yourself petite, but having a rectangle is a bit of an exaggeration. Your body's fine but perhaps you need to eat more if you find yourself a little thin for the usual clothes. Regardless, to dress your age, try long-sleeved dresses with Peter Pan collars. They will flatter you just fine and they're age appropriate. Drawstring tunic dresses are, for me, sophisticated and perfect for girls with curve concerns.
