Does a woman's semen not detach from outside the vulva, and is it obligatory for her to look at her clothes and inside the vagina to confirm the presence of semen due to a wet dream or janabah?

The correct view is that a woman's maniyy (sexual fluid) is discharged just as a man's fluid is discharged, and this has been confirmed in prophetic hadiths. Janabah (ritual impurity requiring ghusl) necessitates ghusl (ritual bathing) in two situations: sexual intercourse, for which ghusl becomes obligatory merely by the joining of the two circumcised parts, whether ejaculation occurs or not; and a wet dream or ejaculation while awake, for which ghusl becomes obligatory if the woman sees the fluid or its traces.