Make her study in the garden is what I say!
Or study in the forest, in Norwegian style ;)
Could we say this sentence using verb "need" with some word? Like: "Hun trenger ...(til?) studere i huset".
I believe "Hun trenger å studere i huset" would be what you're looking for. The difference being "She must" = "Hun må" and "She needs to" = "Hun trenger å".