Ask teachers or parents for help. I have this idea because I see that Ms. Wei Shusheng has this way. Because her current topic is very difficult, it is still difficult to solve it in a short time. Instead of being constantly hit by these topics, try to change some topics.
If you do this, you need the support of teachers and parents, let teachers communicate with parents, make some adjustments for children, and let teachers choose some topics with appropriate difficulty for your cousin to get her out of the previous predicament. This change may be more helpful to improve your cousin's self-confidence and make her grades gradually stable. If it is good, it will gradually improve.
Second, let her understand the significance of learning for herself.
From my cousin's point of view, it may not be appropriate to transfer. Maybe she agrees with the original teaching method of the school, but the current "cramming education" method is contradictory in her mind, which is the "reasonable" explanation you found for her declining grades. But in essence, what she may lack is that she doesn't understand the meaning of learning for herself. No matter what kind of education, study and school are all ways for a person to integrate into society, which she may not realize. If you just complain that the school's education method is not right with yourself, you will not be able to adapt to society well in the future.
It sounds like you should be a student with a little age difference and good study, but she can't understand what you said to her, perhaps because you can't convey to her your certainty about the necessity of study. Why do we study? Who are we studying for? These are the most important things. If you just study hard and don't understand the purpose and significance of learning, then good grades or bad grades are just different aspects of the same thing.
Third, the formation process of these formulas is pushed together with him.
Other situations can also try to do this. One is to review the basic contents of the class again, because the basic contents are gradually improved and the difficulty is gradually increased, but they are all gradually derived from the previous ones. When she is difficult to understand the current problem, she can try to push the formation process of these formulas with him, which may help him better understand the current content. When she reviews, it will be much easier to do the problem again. We can set a time for the problem that we can't meet and ask for help if we can't remember it, so that we won't get into trouble because of a topic.
But learning mainly depends on your cousin's ideas and determination. External forces will play some role, but with her internal initiative, things will be easier to solve. It is certainly not easy to improve in a short time. We should have an accurate and sober consciousness, and be more sure of her efforts. Even if she only does one question correctly, we should see her progress. In the case of being affirmed by others, she will gradually build up her confidence. I'm glad that your cousin is as concerned about her situation as you are. I believe that with the passage of time, efforts will gradually bear fruit.