Does vaginal discharge nullify Wudu' only if it reaches the outer vulva, and what is the ruling on that which does not exit to the outer vulva and does not wet the underwear?

That which exits from a woman's private part (such as menstruation or things that nullify ablution) is not considered to have exited Islamically unless it reaches the place that becomes visible when she sits on her heels. This is sufficient for the rulings pertaining to that which exits to apply.