Donna was a friend of John Winchester who used to babysit the young Winchesters.
Donna worked as a hotel maid in Housatonic, MA where John passed through and sometimes left his sons with her while he worked, on one occasion leaving them for two weeks. She told her daughter Katie that little Sammy tried to tell her what their father's line of work was, but she didn't believe him, at first. Sam told Katie that her mom was the best babysitter he and Dean ever had.
Sam and Dean responded to Donna's call concerning poltergeist activity in their home. She told them it began a couple of months after they moved in as scraping and bumps in the walls, and then progressed into things breaking. Finally, two nights before the The Winchesters arrived, Katie was attacked. Katie showed them her abdomen where the words "Murderd Chylde" had been carved into her skin. Dean reassured Katie that everything would be fine, and the family left for a few days to allow them to take care of the problem. When Dean later mentioned to Sam how well Donna looked, Sam teased him about still having "the hots" for her.
Later, Gary Frankle, after working a spell by which he swapped bodies with Sam in an effort to collect a demon bounty on Dean, revealed to Dean the truth he'd uncovered about the original owner of Donna's house, Isaiah Pickett. While local legend held that Pickett had hanged a young woman, Maggie Briggs, in his backyard for being a witch, Gary's research found that he actually killed her after she became pregnant with their illegitimate child and buried her in the basement of the house. Dean realized that it explained the words carved into Katie's skin.
Dean and Gary went to the house for the salt and burn, and Gary came close to using the opportunity to shoot Dean in the back as he dug up the bones. But, Gary was thrown across the basement by the ghost before he could pull the trigger. He ultimately burned Maggie Briggs' bones just as her angry spirit was about to attack Dean, clearing the house for Donna and her family.