It would be helpful to find a trainer that can work with her in increasing flexibility as well as strength and conditioning. Increasing the strength in her shoulders, back-both upper and lower back, and legs are all important part in stunting and tumbling. It is hard for most trainers to understand and realize what a competitive cheerleader/tumbler does, so it may be helpful to bring a video showing what she does, so they can help her work on muscle groups she needs to strengthen. Some trainers, though are now becoming more educated on the different needs of their clients and their sports/activities.
Sometimes, cheerleaders use the wrong muscles because they become 'habit' and wear and tear occurs on muscles and joints. Strengthening the muscles used in stunting and tumbling will help to avoid the wear and tear on her body-something I'm sure she will appreciate when she is older. There is a crazy fact that the amount of force that tumbling on a mat exerts on the hips and knees is something like 1,000 pounds each time they land!! Increasing the flexibility in her back, hips, and shoulders will help with her tumbling.