Question for Rent Control Office

I rented a room but I have not yet moved in to the room. I have rescind my decision to live in that room because the landlady has a rule that I can live in the single room as a couple with a child. she did not inform me about this rule when she received the rent money. i have informed her about my decision not to live in the room due to that rule, but she is saying someone has to replace me in that room before she gives me back my money. is it lawful for her to say that?