another suggestion was given to me the other day. If you are ok with giving treats.
When you get out on the trail, and she relaxes on her own, give her a treat. Then give some time, when she least expects it, and she is relaxed, and listening, give a treat. That helps to let her know a ride is not all that bad, and if I am Relaxed, I might get a reward. Plus it helps the rider relax a bit, too. Since they know when we are nervous, it helps to try to relax ourselves a lot, too.