Too practical in A transparent lockbox

Sometimes I am reminded of the variation of the human mind. I have witnessed some people in my life who are said to be smart, but they aren’t very intelligent. I have a half-sister who did a degree in mathematics and had around a 4.1 GPA, but she is one of the least aware people I have ever witnessed in my life. She can do all these academic things, but she takes no meaning from them, she just likes getting good grades and validation. She is nearly incapable of taking care of herself on every level from financial to emotional.
When it comes to her family life, she has two children who she only had because she felt it was what she was supposed to do, but she doesn’t enjoy raising them. At every opportunity she will enroll them in after-school activities so they won’t have to be home and she projects who she thinks they should be onto them. Because of how dirty her house was, someone called child protective services on her before and she was given a warning that if she didn’t have it cleaned in 60 days, they would take the children. They are viciously maladapted children, one of them talks in a baby voice as a teenager and demands her mother’s attention constantly, and the other is against everything her mother stands for in that she refuses to go to church, doesn’t want to do activities, and hates math.
It has only been bugging me so much because for Christmas they visited and the resentment she held for her own daughter was palpable. She would reduce her dislike of church and math to ADHD and anything else that her child doesn’t like that she felt she should. All her interests that were brought up were minimized to seem ridiculous, because she likes Pokemon cards and music rather than math and god.
Usually, I don’t enjoy criticizing others for the way they parent or live their life, but she also took a few shots at me recently. In my family, we are mostly people of trades and labour. Three of us have degrees and it is me, my half-sister, and my cousin. For some reason, my sister sees me as a form of competition because of this and tries to attack the things I study. I say that I’m taking medieval literature and neuroscience, and she mentions how useless they are, and that I should do more practical things like math and finance. But if I can make it work and take joy and meaning from it, I don’t see it to be any of her business. She doesn’t necessarily understand “meaning”, just her form of practicality. It struck me because while I don’t take any of it to heart, her kids grew up in this environment of being told what they should like and then what is useless by her standards, and it is devastating that any wrong move will leave them feeling as though they are disappointing her or that they can never be good enough.