I agree with some of the other sentiment. I'm really uncomfortable with the attitude that the poster seems to have that he needs to FORCE his sister into being

I agree with some of the other sentiment. I'm really uncomfortable with the attitude that the poster seems to have that he needs to FORCE his sister into being interested in math. I was the exact same way with History. But, despite being surrounded by junky grade school textbooks, I was still able to do extra research and get involved in math, because I was interested in it. Is she like this in all her subjects? She's not just some blank slate that you can mold into what you'd like - she's a person with her own interests and passions. These may be something that you might scoff at, I don't know, like posting makeup tips on youtube, but that's what she's interested in. You shouldn't try to change it, and doing so will end badly.