Rachel Uchitel and Janice Dickinson can't stand each other and have had several loud arguments in Celebrity Rehab 4, RadarOnline.com has learned exclusively.
"Rachel hates Janice and Janice hates Rachel," a source told RadarOnline.com. "Janice thinks Rachel is an opportunist, and Rachel thinks Janice is a has been.
"They haven't gotten along since the beginning. They get into frequent loud arguments and it's getting disruptive for the others.
"Janice frequently rolls her eyes when Rachel is talking in the group therapy sessions."
As RadarOnline.com reported exclusively Wednesday, Uchitel bolted from Celeb Rehab and said: "I quit" after grueling therapy.
Tiger Woods' former Number 1 mistress bolted for the swanky L'Ermitage Hotel in Beverly Hills, where she spent the night. Producers talked her into coming back the next day.
Uchitel and Dickinson have not gotten into a physical altercation yet.
Rachel's flight from Celebrity Rehab 4 was prompted by a grueling therapy session with Dr. Drew. Erroneous reports claim the reason she left was because she was talking about her father's overdose death from cocaine when Rachel was a teenager. But a source close to Rachel tells us, "Dr. Drew was talking her about her insecurities. Rachel said she can handle being called a homewrecker or a gold digger but she couldn't handle being called ugly or old looking.
"Her identity is wrapped up in her looks. She is obsessed with the way she looks, period."