she is fixated on watching tv (to the point of not interacting with people very often) and criticising dad almost every moment! she has a VERY low tolerance for frustration if anyone says anything she doesn't like or agree with and seems to use temper tantrums to control the situation. dad's coping mechanism is to not rock the boat & always let her be- no matter how cruel or unreasonable she's being. i worry that both of them are experiencing a poor quality of life. help.
We're thinking that the cancer, when she didn't know she had it, had been making mom feel "under the weather" for a long time. She probably just chalked it up to old age, but it had her feeling grumpy and she was being overly snappy with my dad all the time. Kinda like a lot of us...we're pretty nice until we get to feeling bad (flu, cold, bad headache) and we find ourselves being snappy without really meaning to be.
When my mom was finally diagnosed with cancer she became so moody that the doctor prescribed meds to calm her anxiety. They evened out her moods and had the added benefit of making her nicer. You might talk you mom's doctor about what's going on with her, or have your dad talk to them. Hopefully it's not something as serious as a lurking cancer, but this might be a way to even out her moods and give both her and your dad both a better quality of life.
She is not happy, and it's possible that the right medication could make her happier. Do what you can to get her doctor to address this problem. Maybe you could write a letter to the office, telling him/her what is going on, so no one would have to discuss it to your mother's face. I think this is also a risk to your father's health to live with all the stress. Do what you can. Good luck!
I agree, your father could use support as well, don't overlook him.