How do I get good at sports?

I'm starting athletics in Middle School next year for the first time and I've never even played a sport before. My ex-best friend (yea, long story) is amazing at sports and always said I'll never be good at it. I want to prove her wrong and beat her...in everything
At first, I thought this would be easy considering all of our coaches are my mom's best friends and I know them all personally. But today, I found out that my ex-friend has been kissing up to one of the coaches and the coach thinks that's she's going to be the star player even though she knows we have a lot of drama in the past. This is hard for me because that coach is literally like a second mother to me.
I'm also terrified of failure and humiliating myself in front of everyone.
I know I sound like I'm being a jerk, but that girl's a piece of work. How do I get good at sports?
Thanks! If you don't have anything friendly to say, don't reply.

Try to practice alot everyday! Thats what they say anyway

Get into really good shape. Choose the sports that you want to play and start working on those skills now. Also, go for a run every day. Start with a mile and then build your way up. Try to be able to run 3 miles before the season starts. Also, research the sport and watch professional games on TV so you can see the best field positioning. Remember, you will have pre-season practices to learn other things. The biggest thing is to get into shape. Try running cross-country running, nordic-skiing, and competitive swimming. Those sports are the only ones that work all of your muscles, you don’t need to compete in them but they are the best way to get in shape and become stronger. Good luck, but remember not to sabotage your ex-best-friend because the most important thing is team work. It’s okay to have competition between you and your friend but make sure that it doesn’t put your team behind on game day.