A female body type question?!

Best Answer - Chosen by Voters

I wouldn't consider her period being irregular as a sign that she is behind, puberty wise. Many women in their teen years find that their periods are irregular. Women don't typically hold onto the shape they were prior to puberty. At puberty the body shape changes, usually to ripen the hips and breasts to a plumper size. This doesn't always completely occur because of genetics. Some women have less "curves" than others. A good place to look, if possible, is at her mother's shape and her grandmothers' shapes. This can sometimes give a clue as to what she may grown to look like. Since she is 17 though, she is on the tail-end of her growing years but some women find that they keep growing until about 21.

It's either just her genetics or she's not eating enough, hence her body never fully developed.