Is the salary received by a resident female doctor permissible, given that there are days when she has no work to do in the hospital and feels that her time is being wasted?

You must adhere to the agreed-upon attendance and departure times with the renting entity (the state), and exert effort in training. If you are unable to train, or the authorized person refrains from training you, there is no sin upon you and you are entitled to the wage. It is not permissible for you to leave attendance or depart early except with the permission of the authorized person.