jennifer aniston justin theroux heidi bivensNot so long ago women of the world shot sideways glances at Angelina Jolie after on-set sparks that flew with Brad Pitt led to his split from America's sweetheart, Jennifer Aniston. But now, six years later, is Aniston the 'other woman'?

Aniston recently began romancing Justin Theroux, but according to the tall dark and handsome actor's ex-girlfriend, Heidi Bivens, their 14-year relationship had to end for Theroux to start a new one with the 'Friends' star.

"Heidi is heartbroken," a source told the New York Post. "She was completely blindsided. She and Justin had been together for years, they had a home. Then he met Jennifer and everything changed. At first he claimed he and Jen were just friends."

Bivens, a Tinseltown costume designer, was living with Theroux until she reportedly moved out of their home just last weekend. The pair met when Bivens was 20 years old and Theroux was 24 -- when the actor was just beginning his Hollywood career.