I feel like there is something blocking me from doing what I want.

So I am normally a pretty outgoing person. But only beacuse I force myself to be. And normally only around people I feel comfortable with. Like say I'm in a class with people who I don't find intimidating, I can be really loud. Or if I'm in a class with people who I'm friends with. But as soon as a person who I really wanna be friends with and is really pretty comes in I act all shy...(I'm straight) but like I get quieter and feel like their judging me. Like I talk to them and everything but like i act more quiet. And they are the mean girl types, but yet I know they want to be my friend because they conintinue to try and talk to me. I'm in 8th grade, any advice please?