If she is looking for a furnished flat she will have problems as the landlord will assume the cat will destroy stuff. If she is seeking unfurnished it will be worth a shot. Having been a landlord myself from time to time, I have generally been fairly flexible, depending on the individual tenant's situation. For example, my first investment house had a tiny back garden so I said no dogs (basically out of consideration for the potential dog resident). But the tenant had a very elderly dog who was quite sedentary, and I was happy with that arrangement. It is always worth asking, as the rules are there to provide the landlord with an 'out' if they are otherwise uncomfortable.