If you said traditional wedding vows, you promised to “forsake all others.” In this case, you need to let your wife know what you specifically meant was “forsake her mother.” If this happens, you are facing possibly living with your mother-in-law for the next three decades. But you must resist the demands that she move in. You and your wife could offer to help her get some consulting through the National Foundation for Credit Counseling. Since she’s in her early 50s, she still has quite a way to go and she needs to be maximizing her earnings now in order to reap the greatest Social Security reward when she hits that milestone. Whatever her husband’s health status, your mother-in-law needs a comprehensive look at her financial situation so she can plan herself for her eventual retirement.
I hope her “present husband” (nice touch!) has some life insurance. However tenuous your mother-in-law’s hold on independence is, she does work and live apart from you. But I’m afraid promises extracted from a child who’s under emotional duress are not enforceable. A: Apparently since giving birth to her only child, your mother-in-law’s retirement plan has consisted of being supported by her daughter.