Chynna Phillips, Mackenzie Phillips' half-sister, goes into rehab

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Chynna Phillips -- the half sister of Mackenzie Phillips, who revealed a decade long incestuous relationship with her Mamas and Papas founder/father John Phillips -- has checked into rehab. 

"After much thoughtful deliberation, Chynna Phillips has checked herself into an undisclosed treatment facility for anxiety," said her spokesperson Lizzie Grubman, in a released statement. 

"With the full support of her family and friends, she is looking forward to her recovery. We ask that people respect her and her family's privacy at this time."

Phillips, 42, took Mackenzie's side against her mother Michelle Phillips and her sister Bijou Phillips, who do not believe Mackenzie's allegations.