How can a menstruating girl ascertain the emission of semen or a wet dream, especially if she is awake, and what are the implications if she later feels something descending after recalling something she used to do in her childhood?

Nocturnal emission is the discharge of semen during sleep. A ritual bath (ghusl) becomes obligatory for a woman, whether menstruating or not, if she is certain of the emission of semen, and seeing its color is not a condition. A woman's semen is thin and yellow, and its smell is like that of a man's semen. Its discharge is accompanied by pleasure, and followed by a subsiding of desire. Ghusl becomes obligatory upon its emission, regardless of its characteristics. If she feels a fluid discharging after contemplating something that excites desire, then it is madhiy (pre-seminal fluid), which is a thin, white fluid that discharges during pleasure or contemplation. A menstruating woman who experiences janabah (major ritual impurity) is not obligated to perform ghusl until her menstruation ceases, whereupon she performs a single ghusl for both janabah and menstruation. Her ghusl for janabah during her menstrual period is valid, and the ruling of janabah is lifted according to some scholars.