So, my mom keeps making stuff up. What is making her do this?

So recently I ate half of a bar and threw the rest away because I woke up late and had a long hard practice. I had to go to the gym after that and my mom said I am going to cut your bars in half from now on since you only eat half. I explained why I did that and that I don't normally, but she said I had been doing it forever and she even said she remembers telling me, "Eat the whole thing or save it for later." These where my favorite bars and I would never want to only eat half of one a week you had a chance to find me eating 2. There's been stuff like this in the past where I did not have my glasses on since the doctor said I needed to wear them for an hour and she said that I did not wear them at all that week. Yesterday my dad had to fix them (my mom helped) because I was wearing them in bed and rolled over. This thing is new to me but the glasses thing she has been doing for years. She will also go out of her way to be rude to me at a family dinner after I had been so nice to her.She pretended that when I got home I was not downstairs hitting the punching bag till I could not feel my hands. She had also made fun of me and blamed me for this. I never did things my dad did and also my dad would blame me for things she did and other stuff my brother did, so this was just really annoying. My brother stopped believing me because he was never around when anything bad happened. He always makes me look like the bad guy. Sorry for not adding good grammar, it's just I am so annoyed today and it's super late. I can't sleep cause I am still thinking about all the stuff I did for her (I help a lot but she is always saying you need to help around the house more like your brother). I am not sure if this is Alzheimer’s or dementia, but I need help. This is so hard for me because ever since I lost my best friend I have been sad and then recently also lost my grandpa.