What is the ruling concerning a liquid discharge from a girl who feels a desire to marry when she sees her parents closing their bedroom door or when she sees her mother adorning herself?

The desire for marriage is natural, and Allah has made marriage its legitimate path. Allah has commanded those who cannot find marriage to practice chastity (istifaaf). Istifaaf means seeking chastity and exerting all efforts to achieve it. Among the means of achieving chastity are fasting, occupying one's time, and not overthinking about marriage. What Allah has destined will come to pass. There is no harm in informing one's father of the need for marriage so he can strive to facilitate it.