As a coach, I know if one of my girls had a problem, I would want them to talk to me privately and directly if they had an issue. Not text or phone call, but before practice/after practice ask if you can have a meeting. I know a few others said to take your mom with you. I don't recommend that. You are 15/16 years old. Try to talk to her alone first. If you then don't get results, THEN bring your mom into it.
I wouldn't tend to believe rumors, they could be completely false, or completely misinterpreted.
Example, this statement: "pretty much getting mad at me for wanting to be good"
Do you get angry at other girls on the team if stunts/cheers/dances don't go right? Do you say things that are hurtful/could be perceived as hurtful? I've coached girls like this, and I can see the passion for wanting to do good, but they bring the whole team down by berating teammates for not being "good enough".
Take a step back and think about how you are actually behaving, reacting at practice. How is your attitude? Do you complain? Do you play the blame game? Are you saying things to the other girls on your team that may have gotten back to the coach?
If you truly do not think you do any of the above things, then go to the coach and ask what's up. I don't recommend being too confrontational, just say "I noticed that I'm not flying anymore, and got placed in the back, is there something I need to work on to fly again/get moved up front?" If the coach says: "No, there was no reason"...or something along those lines, then I would bring up what your friend told you.
If the coach tells you why you're not flying, or why you're not in front, don't fight it. Address what she told you that you need to improve on at practice. You may not think it's fair, but it's her decision, and her team. You will not always get along with every single person in life, and that's okay, but you should recognize the people that are trying to make you better.
If nothing improves, then I would go through the chain of command, or whatever is outlined in your rule book. For me it's Coach-Student, Coach-parent-student, Coach-AD-parent-student.
I hope that helps! :) Good luck!