I've been asking myself the same question for a long time, and that's also why I am here. I think there's many different reasons. One of them is that she is a typical "Streber". That's a German word which cannot be translated into English without losing some of its fine nuances. It's a person who is extremely ambitious at school, but mostly because they crave short-term validation and praise from teachers. They don't necessarily have a specific goal for which you have to be extremely ambitious (such as becoming a doctor), they just love being the teacher's favourite, and to achieve that, they will tell tales, correct their peers, and use fake kindness to get on.
The fact that she is like this gets extremely evident if you watch her older videos or if you read Erimentha who is the perfect example of a Streber. One could think that over the years, she has lost some of these characteristics because people mature as they get older. But since her social interactions have always been so limited, she has just learnt to hide some of these characteristics, without actually getting rid of them.