Please talk to the coach! Fear is normal and I always just offer a step back from the skill so they have choices and are still participating in class. I had kids in class for months who wouldn't do forward rolls. When it was their turn, I would just have them do a bear walk down the wedge mat so they could get used to being upside down in a safer low risk way. I would always ask if they wanted to roll over but would respect their answer. For backwards, I would just have them roll back part way and push their hands into the mat, but not roll over. Again, I would always ask if I could help them roll over, but would respect the answer. Sitting in a tuck and trying a rock and roll, or doing a candle stick roll (with or without a mat) are other good alternatives. Eventually, they will usually be ready to try. Sometimes they decide not to do gymnastics the next session at some point. Both outcomes are totally fine!
Try to come a little early next class and catch the coach. Say something like, "Hi, I'm Sally's mom and she is really nervous about doing rolls. Would it be ok if she did (one of the alternatives I listed above) until she feels ready?" Then you could tell your daughter "Coach Jill says it's ok if you aren't ready to roll yet. You can do (xyz) instead when it's your turn. She might ask you if you want to try, and you can say , 'yes, please help, or no thank you' or let her know when you're ready." That way everyone gets on the same page.