My MIL who’s 91 yr old and widowed is narcissistic and lives with us. Having problems getting her to follow house rules. Any advice?

From your profile: "Retired office manager/dental assistant for 21yrs...had to retire because of complications from cancer...many health issues myself...my widowed MIL 91yrs lives with us now...she’s narcissistic...my husband still has a year and a half to go before he retires"

Why is someone with significant health problems taking care of someone who is (also from your profile) ..."91 years old, living in my home with age-related decline, anxiety, depression, hearing loss, incontinence, mobility problems, and vision problems."

I take it you are doing the bulk of the caregiving? Again, WHY? Did you agree to your MIL moving in? How long has she lived with you? Don't expect her to change. Rather, you must change the situation and what you will put up with.

What does your H say about HIS mother and how difficult it is?

What are the specific rules is your MIL ignoring or refusing?

Profile mentions incontinence, vision & mobility problems. Would these be barriers to keeping the rules eg being unable to see well to clean up the kitchen after making a snack? Being unable to walk well enough to put rubbish outside?

Or is there a cultural/generational expectation you (as DIL) should be her maid?

If the former, work with her for comprimises & solutions.

If the later, hike her rent up.
Way up.

When my mother moved in, she drove me BATTY with not following house rules - the same ones that she taught ME while I was growing up.

Add to that a whole bunch of other behaviors that stressed me out so bad, I became bedridden, I was despondent.

The kind people here advised me to consider that she may have dementia. It was a series of lightbulb moments.

Yep. She was well on her way into moderate dementia. It explained (but didn’t fix) all the behaviors that were making me crazy.

Since you do not mention Dementia as part of MIL's diagnosis you sit down and tell her: Actually your husband is the one that should sit down and discuss this with her,
"Mom, there are House Rules that you need to follow if you are going to remain here. If you can't follow the rules we are going to have to look for another place for you."
Now if your husband will not do this or does not agree with the "follow the rules or move out" idea then your only problem is not with MIL but with your husband.
You do not indicate what problems you are having and adding those details might help.
How does your husband feel about this and does he agree with you?

Facility time for her.

No hope. Narcissists don't change. Plus there's the family dynamic, which isn't in your favor. Start looking for a facility where professionals can take care of her.

You may need to walk her through the rules. Large board with written schedule for her, next to a large print calendar. Also, may need to remind her daily of the daily tasks.

Makati, what happens is the adult/child dynamic. Once a parents or in-law moves into a grown child's home, that parent once again becomes "the boss".

For some reason the parent only sees the grown child as a teen or young adult instead of someone who is not far from being a senior or is a senior themselves.

As others here have asked, what house issues are the issues?

I think you may have guess that this would be the case when/before you took in your MIL? And now it IS the case. I think, in all honesty, that we cannot change others. We can only decide whether we choose to live with them or not.

HI Makati - is there any chance you can kindly elaborate on what the situation is - so that others can provide the proper advice? (such as, what kinds of problems are you facing with MIL..specifics)?