How can a skinny petite young woman like me gain some weight/get thicker?

I’ve been skinny all my life and I’m tired of it. I know you bigger girls think I’m nuts but hear me out. Not every girl who is skinny/slim are happy with their bodies and not every girl wants to be skinny. Men like healthy looking women, not thin rail women. It’s just the truth. I was skinny until I hit puberty. I’m slim and curvy. Im still slim and I wanna put on at least 20 pounds. I’ve always envied thicker, curvier women. I hate being slim. My mom laughed at me when I cried and complained about my slender legs. She told me, “You listen here child, when you get older, you’re going to want those beautiful slim legs and figure. No use of crying over it. You’re going be glad that you have those beautiful slim legs and there’s women that WISH they had that.
Yes mom but it doesn’t mean I’m going to be happy about it. I want to gain weight and be thick. Im sick of my thigh gap and I want my thighs to touch. See? Not ever female wants to be thin. Gaining weight doesn’t always mean unhealthy and slender doesn’t always mean healthy. Thick is better. I am 5’0” and currently 102lbs. I can’t gain weight. I don’t wanna be overweight either. I wanna get to about 120lbs or 125lbs. I have a tiny built. I’m very active even though I work and I’m a college student.