My wife, who is 40, has taken to wearing very suggestive clothes, flirts constantly with other men, is still involved in her PA and appears to be in an EA with another or perhaps the same man. She goes to the pub 2 or 3 times a week and sometimes stays out until 6 o'clock in the morning (when she wouldn't go out to the pub at all before). On New Year's Day she was out until 8. When she's not in the pub at night she lies on the couch listening to music with complete disinterest in the children (and, of course, myself).
DBing aside, have you talked to an attorney in your jurisdiction, to better understand what your rights and responsibilities are here? I'm concerned about your children, as it's not emotionally healthy for them to be in this environment (what happens if one of them wakes up at 3 in the morning and wants their mother?)
If your wife wants to carry on like a single woman, my advice would be to give her what she thinks she wants. But it wouldn't be in my house, with my kids.
