Gary Collins and Wife -- Separated: She Needs a Break

Gary Collins' wife of 43 years needs a time out in her marriage to the TV host ... TMZ has learned she filed Monday for legal separation.

Mary Ann Mobley -- who won the Miss America title in 1959 -- is "miserable about the whole situation" ... this according to her rep who spoke with TMZ.

Mary Ann is undergoing chemotherapy and radiation as she deals with stage 3 breast cancer. Mary Ann's rep tells us Gary is depressed about her illness and they both felt they needed a break.

The rep says no other person is involved in the separation.

Gary has had his own problems, after being arrested 3 times and convicted twice for DUI.

The date of separation is listed as October 1, 2010 -- nearly a year ago.