What is the optimum weight for young women?

When I was younger I was very skinny, but people mentioned that my figure wasn't womanly. As I grew older I filled out and have an average, womanly figure, except now my mother keeps sitting down with me and trying to point out to me that I am not thin, now, but average, and with a womanliness, and I should accept that I am no longer in a thin category. I feel like she is saying I should be skinny, because that is what the media desires, but I also know from past experience people think women should have womanly features like big breasts, and a bit of curves, etc. I am thoroughly confused, it seems like people change the rules all the time. Is my mother saying I should lose weight and go back to being a skinny twenty year old at any cost? I am happy with my average weight, I am by no means fat, and at least I have a chest.