Is what the questioner habitually does considered masturbation, and is ghusl obligatory because of it, knowing that nothing is emitted from her?

The act of masturbation mentioned, using water to release desire, is prohibited masturbation. It is not a condition for it to be done by hand. If semen is discharged as a result of this act, then ghusl (ritual bath) is obligatory; otherwise, it is not. You must repent to Allah Almighty and abandon this habit.