A friend of mine had something similar, it was a bit of a desperately need flat, this one is affordable situation. The flatmate who had the open room started out fine, but then got extremely controlling and health cranky. Like she decided she was going to start going to bed at 8pm and you weren’t allowed to use the kitchen after 7pm, nobody was allowed visitors, nobody was allowed to cook food she thought was “fattening” or had “too many smells” etc etc.