Speaking in an interview with WBRC-TV, Angela Harris said "there has to be someone who knows" what happened to Aniah Haley Blanchard, 19, of suburban Birmingham.
"We have to have her back," she said. A social media message sent by Blanchard to her roommate indicated she might have been with a male before she disappeared, Harris said.
RELATED: Damaged vehicle found in search for missing college student
Husband Walt Harris, who fights with the mixed martial arts fighting organization, said relatives don't understand what might have happened to the college student.
"There are just a lot of things that don't add up for us as parents," he said. "We just really, really want to know."
The Southern Union State Community College student was last seen Oct. 24. Police later found her damaged car in Montgomery, about 55 miles.
A statement from Auburn police Thursday said evidence found inside the vehicle indicated the young woman had been harmed and was the victim of foul play.
The young woman's parents spoke after the president of UFC, Dana White, tweeted a video saying he was offering a reward of $25,000. The money was in addition two rewards of $5,000 each offered by an anonymous donor and the state.