I'm not sure. It's always dangerous to try to diagnose someone else. There was an article in Phychology Today that brings up just this point.
But that being said...
I think it is a reaction to the stress she has been under in the past years. - Father Died - 3 small kids - New house, town, friends - Mother has cancer, now terminal - Stressful home remodeling - Husband (me) working long hours and traveling - Stress about aging and her stalled career
I think she has regressed to wanting to be a teenager again. She is acting like the stories I heard about her from the high school and early college years - non-thinking, impulsive, overly trusting, irresponsible.
Me 42, W 39, S8, S6, S2 M 11y, A & ILYBNILWY 11/08 Walking away from a bad situation.