My mom was positive, sweet, outgoing and usually supportive.
Nothing we say is right, nothing suggested is a good idea.
Complaints about lack of sleep but sleeps a lot day and night.
Doesn’t eat at meals, too much food, not really hungry doesn’t feel good, but immediately after meal snacking.
Its difficult, but refrain from making suggestions and giving her the opportunity to disagree. If she does disagree, don’t argue, just drop it. If she complains about not sleeping, “I’m sorry you didn’t sleep last night, Mom.” If sne complains about too much food, make her plate at the counter and put bird portions on it. Don’t set bowls and platters on the table in front of her. The rest of the family can also serve themselves at the counter. If she snacks after supper, keep healthy snacks available. Store the junk food where she can’t get it. It’s psychology and it’s not easy but it can work.
Regarding sleep. My parents use to brag about how they only needed 6 hours a sleep. They forgot to add in the hour nap after breakfast, the hour nap after lunch, the hour nap before dinner, and the two hour nap after dinner. They were always awake to watch Johnny Carson :)
Ah, food. As we age we can lose our sense of taste. That explained why my Mom's grocery list had so many sweets listed, probably the only thing my parents can actually taste. I am finding that with myself. And if our parent isn't exercising, their appetite will drop.
I assume your Dad has passed on. If your folks had a wonderful life, then your Mom misses the love of her life. That can make anyone feel unhappy, and bitter.
At your Mom's age, 86, she probably cannot just jump in the car to drive to meet friends for lunch. And her friends have either moved away or passed on.
So this is something to take into consideration whenever your Mom is down in the dumps.