How can I gain weight?

I'm a 16 year old female, I'm about 5'2 and barely weigh 100 pounds and frankly it disgusts me. I am a vegetarian, because of my personal beliefs, so eating more meat isn't an option. I do replace my meat though, with other sources of protein. I know I have a high metabolism, because my mom had the same thing or whatever I guess, so I'm just wondering, serious answers please, how can I gain weight despite my hereditary high metabolism and vegetarianism?