Dorotea is another madwoman (this town is crawling with 'em) but unlike fellow crazylady Susana San Juan, she's not married to Pedro Páramo, and she's really poor.
Miguel Páramo, Pedro's son, hires her to find girls for him to either hook up with (if they're willing) or rape (if they aren't). She tries to confess this sin to the priest, but he thinks she's too crazy to be punished for her sins.
In the Spanish literary tradition, a person who makes matches or who helps men capture the women they want is called a "Celestina," named after a match-making character from Fernando de Rojas La Celestina. Dorotea isn't ever directly called a "Celestina" in this novel, but that's pretty much what her job was. Dorotea describes what she did for Miguel to the priest:
"Well, that I was the one who rounded up Miguelito's girls."
"You took them to him?"
"Sometimes I did. Other times I just made the arrangements. And with some, all I did was head him in the right direction. You know, the hour when they would be alone, and when he could catch them unawares." […]
"How many times have you come to ask me to send you to Heaven when you die? You hoped to find your son there, didn't you, Dorotea? Well, you won't go to Heaven now. May God forgive you." (60.84-92)
The priest is totally right: When Dorotea dies she doesn't get to heaven. Instead, she's stuck in her coffin (which she ends up sharing with Juan Preciado) listening to all the other ghosts talking. She can't hear them very well, though, and has to get Juan to tell her what they're saying. Ugh. Dead and hard of hearing? That's doubly sucky.
When she's alive, Dorotea wants very badly to have a son, but isn't able to and so wanders around town acting like she is carrying a baby. It's super-depressing. One night she dreams that she dies and goes to heaven and finds out there that she is unable to have children. Poor Dorotea never ends up getting to heaven, and never ends up having a kiddo.
Dorotea's various names also add important clues about her character. Damiana calls her "La Cuarraca," a nickname given to people who limp. We can guess that, besides being crazy, she also had physical problems walking, so she's doubly disabled and that much more defenseless within the community.
And when Juan Preciado finds himself in the coffin with her, he mishears her name as Doroteo, which is the masculine version of her name. This adds to the sense of Dorotea as a failed mother, since her femininity (best represented by motherhood, at least in the world of Comala) is not complete.
Life is super-hard for poor Doratea, but at least she gets a pretty nice coffin-mate to share eternity with? Silver lining? Maybe? We want something good for poor ol' D.