Sandra — here are some truly disturbing details about yet another Jesse James affair! His third mistress, Brigitte Daguerre, told friends that Jesse fired her after she refused to continue the alleged relationship!

Jesse James‘ alleged third mistress, Brigitte Daguerre, worked for him at his West Coast Choppers shop in Long Beach, Calif. — but not for long.

Brigitte, who was reportedly hired to do styling work for a West Coast Choppers photo shoot in 2008, was let go because she refused to continue her relationship with Sandra Bullock‘s husband, according to Brigitte’s former boss, Ken Marcus.

Brigitte worked for Ken — owner of Ken Marcus Studios in Hollywood, Calif. — for nine years.  And he tells HollywoodLife.com EXCLUSIVELY, “When Brigitte didn’t want to be intimate [anymore], Jesse dropped all professional involvement.”

Ken says that he “is like a mentor” to Brigitte, and she would often talk to him about her year-long relationship with Jesse. “I’ve known Brigitte for [nine] years. I was aware of the incidents that happened with Jesse,” says Ken. According to Ken, Jesse and Brigitte were intimate with each other, but “Jesse would kick her out” immediately after they were together. “Brigitte didn’t feel like there was any [emotional] reciprocation on Jesse’s end,” he says.

Ken confesses to us that he was not fond of the way Jesse allegedly treated Brigitte: “Jesse would have her show up at West Coast Choppers after everyone else would leave.”  He even claims Brigitte didn’t know that he was married to Sandra Bullock. “I’m not sure she knew he was married, because he never wore a wedding ring.”

After one year of the secret meetings, “Brigitte voiced her displeasure about the way Jesse was treating her,” says Ken, adding that Jesse stopped asking the photographer to work with him “after Brigitte refused to be intimate with him.”

We contacted both Jesse lawyer and publicist, but haven’t heard back from them as yet.

Brigitte, a photographer and owner of Poshgirlvintage.com — an online clothing store in Canoga Park, Calif. — claims she and Jesse shared 195 text messages, “many of them extremely graphic” over the course of a year. Still, Ken is very loyal to his former employee. Brigitte “is a very legitimate person. She is bright, talented and serious minded. A talented photographer,” he confesses.

– Chloe Melas