I'm so ugly next to my younger sister?

You dont have to do anything. You have friends already, so you're likable, and you are described as cheerful and bubbly. It isn't actually a competition with your sister. No matter how much she is admired, there are plenty of people in the world for you to like and who will like you back. When you meet the right guy, he will call you beautiful. Your showy sister attracts a lot of attention, but that's it. As you say, she doesn't actually do much with the guys she attracts, so it's really just attention, and nothing more. Attention isn't close friendship, genuine liking, a relationship, or love. You have as good a chance as she has, if not better, of getting those far more important things. People who are confident of getting attention often become lazy, expecting to have to do nothing to keep friends and boyfriends, but that doesn't actually work. I think you are far better off than you realise, and with a new pool of potential friends and boyfriends at college, I think, if you relax, you're going to have a great time.