Congratulations to your daughter on her season! My daughter also tends to get nervous before meets but usually calms down by the time the meet starts. Here are some suggestions that have helped her:
1. The day of the meet, especially if the meet is in the afternoon, try to keep a consistent schedule as if it were a regular day. Breakfast/lunch should be what she usually eats. If she usually does another activity in the morning, make sure she does it. Or try to do something that will distract her from thinking about the meet - work on a craft project, build a Lego set or a puzzle, go for a walk, hang out with friends... anything but sit at home and stress about the meet!
2. Don't think of the meet as a "test" or "performance" of any sort. It's just a way to show where her skills are on that day. If she scores well, that's great, but don't make too big of a deal about it. If she falls and messes up and does not score as well, it's also not a big deal.
3. Related to that, we've spent a lot of time talking about judges, and the fact that judges are not there to criticize her. They want her to do well, and they are there to give her information about how her skills are going on that day, and what skills she should work on.
I have also found that much of her nervousness has to do with her confidence, and much of that has to do with experience competing. The more practice she gets competing, the more it will seem like competing is "normal."
I hope this helps! Good luck to your daughter, let us know how her next season goes!