A concerning enough number of serious female high school runners that end up in the D1 ranks appear to be deliberately skinny. I never observed them to perform better than their chunkier (but the ones that are hard-working, talented and athletic; obviously there will be chunky ones that are just lazy/sucky/untalented) teammates.
Being slender when done right--achieved through sustainable means and not the anorexic/compulsive body image instinct--is certainly an asset for top performance. But that takes a lot of knowledge and parameters and everyone is on their own journey to get to that point.
I say, keep doing what you're doing--don't worry about them. Keep a healthy weight, live a good lifestyle, work hard and stick with a reasonable standard of beauty. No need to envy them at all.
They have the same insecurities/social desires (inc. boys) that you do and they'll end up abandoning their super skinny compulsive pursuits in due time, to 'abandon' themselves to the chase like the rest of society.
That is just speaking about college runners and what I've seen. The majority of high school female runners I've seen and at my former high school were very healthy and wholesome looking, and, as far as I could tell, exceedingly happy with their social and school lives. And the ones who were stars, athletic success came to those who put in the work, not starved themselves.