I think it is nice that you have bought her new linen & thought about that extra stuff to make the space nice for her, but without a door, I'm not sure that would offset the downside. I guess it depends on how reasonable she is. I'd probably be inclined to ask your parents to find alternative accomodation (hotel/tent in backyard whatever, or playroom if you must) and give DSD the "cupboard". Privacy is a big issue for teenagers (based on my limited experience of myself lol).