Denise: Heather and I Will Never Be Friends Again

“Extra” was with a brave Denise Richards at the Associates for Breast and Prostate Cancer Luncheon on Wednesday, where the star opened up about her 53-year-old mother's battle with incurable kidney cancer.

Denise was honored at the lunch, and she dropped this bombshell to “Extra:” “For years my mom was misdiagnosed. Her doctor told her it pre-menopause, and not to worry. Had they caught my mom's cancer in stage one, she would have been cured.”

Her mom's cancer has now spread to her brain, and doctors have said it is incurable.

“My mom is still fighting, and I'm in awe of her strength,” Denise said.

Denise knows about being strong herself – she recently helped her boyfriend Richie Sambora get through his own tragedy when his father died of cancer.

Richards also opened up about her romance with the rocker, telling OK magazine she did not steal her former friend Heather Locklear's husband.

“I didn't have an affair with Richie during his marriage,” she insisted. “I wasn't her friend who said, 'By the way I'm sleeping with your husband.'”

But Denise said that she and Heather will never be friends again.

For now, however, the star told “Extra” that the only relationship she is focusing on is the one with her mother.