In Spanish it’s when a girl doesn’t shower much or clean herself. Or When she’s nasty in other type of forms.

when you're hungover as shit after a spending a night drunk as a skunk

One of several definitions referring to a woman who is sexually "open" to try anything her partner wants in the bedroom or other places including public locations, i.e. elevators, bathroom, kitchen, etc.

It has been suggested that that the ultimate fantasy woman girlfriend acts like "Queen" in social circles but when it comes to pleasing her man becomes a sexually, no holds barred, "Mugrosa!"
I would refer to the movie, "Fatal Attraction" to get a partial idea of a "Mugrosa" is capable of!