Beauty is in the eye of the beholder, but you can waste your life trying to please the wrong beholder.
I understand where she is coming from - I was an underweight child, who after being molested by a neighbour, doubled in weight and became an overweight child and even when I wasn’t overweight and looked good in my late teens and 20’s - I still thought I was fat. It wasn’t until years later looking at the photos that I saw I actually hadn’t been. By then I had married and had children and never lost the weight again, and I don’t care, I don’t feel comfortable skinny anyway. My grandmother told me, 'no man wants to come home at the end of a day and land on a pile of knobbly bones, they want something nice and soft and warm to sink into.’ I thought she was just trying to make me feel better about myself, at the time, but think now that maybe she was right. The man of my heart was a bit of a chubby chaser.
The truth is that true beauty is the radiance that comes from the light within, and lasts far longer than the fleeting fleshly beauty of youth. So if you're beautiful, and every woman is in their own way, enjoy it while you can, but don’t expect it to last and don’t waste time worrying about it, if you think you aren’t. Life is too short to waste time, beating yourself up on that hamster wheel. Instead focus on growing that inner beauty and relationship with Jesus that will last beyond your external looks. Only really shallow men, not worth keeping. will care about how you look. While good looks might attract them for a while, it's how you treat them and make them feel about themselves that really matters.
Remember you won’t find inner beauty and peace by comparing yourself to the air-brushed models and celebrity pictures in glossy magazines. The only one you should compare yourself to is you. Ask God to remove the scales from your eyes and show you what you look like in His eyes. The only healthy and lasting definition of beauty comes from God because he judges people by what is in their hearts.