There's trouble in "The Hills," as Heidi Montag's mom is none too pleased about her daughter's secret Mexico wedding to Spencer Pratt, the new issue of Us Weekly reports.

In an exclusive interview from her home in Crested Butte, Colorado, Darlene Egelhoff tells the mag that her daughter blew off Thanksgiving with her family to stay with her co-star/new hubby in Cabo San Lucas, where they eloped on Nov. 20 to the surprise of the family.

"He's manipulative and seems to have power over Heidi," she continues. "Spencer has tried to cut everyone out of her life. I've been honest with Heidi, and it's caused our relationship to decline. I'm more devastated about that than the marriage, because I'm confident the marriage won't work out."

Perhaps Egelhoff's reaction is no surprise, as she and Spencer have clashed on-camera for all to see. "God says love your enemies, but I never expected it to be my son-in-law," she bristles. "[I give the marriage] six months. I think it's the biggest mistake Heidi's ever made."

Heidi tells the magazine that she didn't invite her mom to her wedding because she was "starting so much drama" and adds, "She should be happy I found someone I love."

And what does Spencer have to say about his new mother-in-law's comments?

"I think her mom needs to take a real fat chill pill and be happy for her daughter."

Watch ET for all the latest news of Heidi and Spencer!