Girls suffer mental blocks far more than do boys. Most are backward skills. Often they appear during competitive season or during other stressful times.
Terri Laymon:
… There is something to be said about ‘putting in the numbers’. The body needs time …
Moving through skills too quickly can cause a breakdown of acquiring the confidence and achievement of successes the mind needs in order to move forward. Sometimes slowing down is the best medicine. …
Especially don’t rush backwards skills. Use as many progressions as possible where there is minimal risk of injury IF something goes wrong on a backward skill. (e.g. Flyaway)
Gymnastics Coaching.com 