Body and weight loss?

ok. I am relatively slim, but curvy. (scarlett johansson BODYTYPE) I don't mind having curves, it's good not to be too skinny or all bones. But I'd never really been an athlete or exercise regularly, so I've put on enough weight (tum & hips.) I've started going to the gym since last week and I'm also following a healthy "nourishment". What I'm worrying about is that even when I lose most of the extra kgs, I'm not happy with the whole image. Is the gym going to help me lose most of the fat and tone up just like i want to? I don't want to be stick thin, or anorexic, but I really want to have a nice body, to be slim and in shape. Is it possible that I could never make it? My mum told me I'll never make it cause it's my bodytype and I better not even think about it or try, but she never encourages me and doesn't know ANYTHING about weight loss, or gymnastics, so anyone...?