Lindsay Lohan’s bitter love rival has spoken out with claims the troubled-actress induldged in a heated rehab stairwell sex romp with her new beau Riley Giles.

Bree Tierney – who claims to be Giles ditched fiancée – claims that the Mean Girls actress ruined her life by pairing up with the snowboarder at the Cirque lodge rehab centre in Utah, where they were both seeking treatment for substance abuse.

She tells U.S. magazine Star: "Lindsay Lohan stole my fiance and wrecked my life. I loved Riley and Lindsay stole him from me.

"I've stuck by Riley through the good and the bad. Even after a car accident in Las Vegas, when Riley was arrested and I was left at the scene. That was his third or fourth DUI. We knew then he had to get help.

"So he went into rehab, and I waited for him. We lived together for three years and planned on being together.

"But then he confirmed that he had sex with Lindsay in one of the stairwells at Cirque - that was it, we were done."

And the blonde beauty has dismissed any chance of a reconciliation.

"There's no way they are going to last. He's just looking for publicity. He's got Lindsay to get attention for his so-called snowboarding career. He's using her, and she's using him - nice, huh?

She concludes: "But I should thank Lindsay. She ruined my life but also opened my eyes. She actually did me a favour. Riley and Lindsay are perfect for each other."

Be sure to check out Lindsay Lohan dining with the paparazzi by clicking here!