What to do with 84 year old Mom who does things we ask her not to for her safety or ours?

She says she is going up and down stairs safely - yet - the minute I even step out for groceries - she fell cause she was trying to get a coat down not using her cane. She fell trying to carry stuff up stairs after I asked her to not do that and went over it for 3 hours. She is stubborn and the door is closed on her receiving anything from me. If I ask - she will DO it. I asked her NOT to feed the cat on the counter - close to the stove also - and after I go to bed - she will sneak down and do just that. I can't trust her and I try not to ask things because she will do JUST THAT one thing and I don't want her to hurt the cats. My husband is at his wits end with her dishonesty and refusing to accept responsibility for any wrongs. I am SHOCKED this is my mother. I guess I was stupid my whole life cause I thought she was nice. I had her tested for dementia but - she is fine - so there is no physical reason for her being awful. We do EVERYTHING for her - she has every convenience and need met - I feel perhaps I've done too much for her her whole life and created a monster now. I 'took care' of her for the last 30 years after my Dad died. I was free so moved back with her. I am now married and we moved to her because she got macular degeneration and she just insists on being obstinate and sneaky. After pooping all over the kitchen floor with a gastro attack - which she tried to hide from us saying 'nothing was wrong' but my husband smelled it - I got it all cleaned up sanitized and finally got her to bed that night. I flopped into bed and found her - she'd snuck downstairs cutting up a Subway sandwich lunchmeat sandwich to try and OVERFEED our obese cat (borderline diabetic). I could not believe it!!!!! She had hidden food in cabinets - her room- just REFUSING to help the cat saying the doctor doesn't know what they are talking about - she LOVES him so FEEDS him. This has fractured our family and respect and trust. I cannot trust her and she doesn't care about either of us at ALL. We are important to what SHE needs out of us. My husband is expendable in her eyes - I am the CHOSEN. My other 2 sisters don't bother - one drains her financially and the other totally dismissed her from her life - she said she 'couldn't do it anymore'. She drained my mother financially also. I have 2 people in my life I love and they are battling - my mother is wrong - yet she is old and I cannot find it in my heart to take extreme measures with her such as a psychiatrist or talking to the Pastor about/with her. Yet - My husband physically cannot take any more - period. I will not let her sacrifice him. She never left her mother off her pedestal her whole life - I don't know how my father stood it - I will not treat my husband the way they did my father. Her mother (my grandmother) threatened my father if he got my mother pregnant and 'put her through' anything again. Her mother (my grandmother) also would visit and not eat a sandwich with my father or let him get her anything. He would leave food out for her after his lunch and she would sneak in there like a little obstinate mouse and eat. He NEVER EVER responded negatively to this. He was a minister and he did say that she would never bring him to sin against her or the situation. He wrote her a letter about the family's activities cause she was alone - every week until he died early at 54. I am going to have her tested physically to make sure - but I think she is JUST FINE physically and just hateful emotionally and I am not going to let her ruin our life - yet - I need to take care of her - someone who lies and can't be trusted. Only time will fix this it seems and that is sadder than sad. We are going to talk to our Pastor - my husband and I - as a major concern now is that HE has pent up upset (he's been sick for a year and a half and doctoring) and he might get bitter - I will not let this happen - she couldn't care. I feel I need to save us and she better get on board cause no one is required to give up their life for another's obstinate foolish expectations. Without me at her 'beck and call' coddling her - she gets nasty and does things she shouldn't - it's a pattern tried and true. I couldn't have believe eldercare/caretaking could be such an awful experience. It seems what I know of my mother and elders and people in general could fit on the pointy end of a pin. Without God I would truly be hopeless - but - God does his best work in these terrible situations - so I'm going to see what we all can learn THROUGH it. I think maybe my mother who seems to miserable might even find a better life - such as it is - than she ever expected. She stays isolated, doesn't care or call anyone, she has macular degeneration and it took a lot out of her quality of life - we have gotten books on tape, the camera at home, take her anywhere she wants - but it doesn't fix anything.