What is my mother up to?

She always seems to know how to blame me - first of all, though, she constantly seems to be trying to make a fool of me, no matter what I do. It's undermining my confidence. She makes me feel like I don't have the ability to think - she always says "think about it," like I'm an idiot. She makes me feel like I'm "slow", my mind may be on something greater, like the next step in the process, but she makes me feel like an idiot for not doing something basic, like not putting out the tea cups, yet, when I've only just poured the tea. It seems like she uses each situation, as an excuse to make me feel ridiculed, or mentally slow. I gave her ice cream I'd bought for her and Dad out of generosity, and said, "are you going to take back all the belittling things you've said," and instead of saying, "oh what do you mean?" she laughed, and said, "yeah". She always has a smile on her face, that sort of looks smart, bitchy. Tonight, when she opened the door to see the cat, she hit him, because he happened to be out of his basket. Even though, I wasn't there, she managed to blame me by saying that I should have "closed the door, more properly." This is maddening. She couldn't admit that she was simply unobservant. I finally decided to stand up to her, after trying to give her the benefit of the doubt, all evening, and said, I'd had enough of her, I'm leaving, she said, "good."! It's like she's so uncaring. Nothing means anything to her, she just laughs.