Without looking to turn the paranoia up, this someone might be a girl friend or a boy friend. I know someone that got shafted by his wife's new fella, he coached her like a conductor of an orchestra, and when his money had run out, the new fella was out of the door and onto his next victim.
Got to keep your cool, one slip is all she is looking for, then it's a well trodden path to frame you as some sort of coercive controller. I did like the gambling shout a few posts back. Has she been a lady of leisure for the marriage? This isn't me suggesting homemaker isn't a job of course, only that middle age, empty nest syndrome, a new squeeze, dissatisfaction with career choices, can all be a part in why things have all of a sudden turned sour.