Is a girl's prayer permissible if she finds traces of urine on her body after waking up from sleep, even without wetness, and is ghusl (ritual bathing) obligatory for her in this case?

Dried urine residue must be washed off, as long as it is not semen. If the questioner is certain of the presence of urine, she must wash it off. If they are mere doubts, she should not pay attention to them. The questioner must make up the prayers she performed while knowingly contaminated with impurity, because the removal of impurity is among the conditions for prayer.