How do I respond to a girl who is unhappy with her body due to weight gain?

I have a small crush on her. It’s also not a bad amount of weight she is still within a safe range but it wouldn’t hurt her to lose some. I still think she’s beautiful. I don’t want it to become her habit to look to others to say she looks okay. I’d like to make her feel good about herself but do it in a way that doesn’t cause a dependence on others opinions.