Is this dementia?

My very independent and self-reliant 97-yr-old widowed MIL started making weird statements and accusations back when she was in her 50's (which is when I married her son) . . . and she worked until she was 82! But what she was doing was a continuation of 'little things' she'd been doing all her life so we couldn't tell when or if the 'little things' started replacing reality. Like several simple decisions were based on "something a lady on the bus told me was a good idea."

Many years ago my husband and I had to move into her home (we converted the basement into an apartment) to take care of her two elderly older sisters who lived in the 2nd floor flat -- MIL lived on first floor. MIL was very jealous of the attention they were getting and was mean to everyone. Screamed at the parametics when they came to take one aunt (congestive heart failure) to the hospital. Would pop out into the stairwell hallway to demand where the other sister was going whenever she would try to leave the house. Snarled at us when we would go up to clean the apartments or deliver meals. Once the sisters had passed away (both in the early 90's) she became even meaner and more self-centered. She continually accused my husband and I of trying to steal her house from her (mostly to her other son), accused us of 'freeloading on her dime (usually in a public place) and over the years made a point of coming outside and screaming at us to stop cutting HER grass or shoveling snow from HER walkway, because, of course, this was HER house!!!. She ripped out the Christmas decorations across the front of the house one year the day after Christmas because "Christmas was over" . . .makes a point of trying to ruin every holiday she can, the list goes on.

I have to keep reminding myself that this is just more of what she has always been since I've known her and not take it to heart, but it is painful to see the affect it has on her son. She drove the other two children away with her meanness so even if they wanted to help it would be difficult. They are there for us if needed.

Fortunately at 97 she enjoys relatively good health and can take care of herself for the most part and her little dog. We both hold full-time jobs, maintain the house, pay the bills and make sure she has food/meals, gets to weekly hair appointments, etc. Her stove was shut off about 8 years ago because she kept forgetting how to use it properly and we were concerned that she would harm herself. I finally removed her ID and bank cards from her purse because she kept hiding them, usually about the time we'd need to go to the bank to cash her social security check which she also would hide at will. . .and last week I had to call the doctor to let him know she had decided she no longer would see him since she didn't have to take the pills he'd prescribed for her high blood pressure because HE had had told her she didn't have to if she felt ok. (She insists that I give her HER pills in a cup every morning or she starts slamming doors until I leave them on the stairs -- but she won't take them.)

Our "pulse points" are that she gets up every day, takes her pill cup from the stairwell where I leave it, feeds herself and her dog, dresses herself and has no tendencies to wander. On Saturdays I take her to the hairdresser, breakfast and grocery shopping. Other than that we leave her alone. She many times won't answer the door if I knock but I can hear her moving around, so that is intentional.

Is the dementia, or is this the action of a very very spoiled person? We can't tell!