Luna has two built in igloo things (part of the shelves) which she very, very rarely uses. Most of the time she sleeps in an open nest, or in her toilet when it's hot.
I've tried a number of houses, the only thing she slept in for ages was a cardboard box >.<
If you buy a wooden house, ensure that it has an open bottom (ie no bottom to it) which will prevent pee from soaking into the base. I'm not a fan of plastic ones because of the condensation that can build up.
If I were you, I'd take all the houses out that she doesn't use/that are unsuitable, give her a massive handful of bedding (I use shredded toilet roll for nesting material) and let her make her own nest