Mercedes has two younger siblings, Tucker and Beth. Mercedes was apparently promiscuous in highschool, she jokingly claims she slept with half of the student body. She was been gone from Purgatory for 12 years, which if she left right after highschool graduation, that would make her 30 years old. She has since become a real estate developer. The reason she comes back to Purgatory is because her parents died, leaving her and her siblings all their money. Since Gonna Getcha Good, The Widows have been keeping her captive in the Gardner mansion basement. One of them has stolen her face and took over her life.
The two girls apparently bonded in high school, being the two most hated women in Purgatory, possibly because both slept with a lot of their classmates.