Evicted for pet in apartment

My friend was just evicted for having a cat. Her lease nowhere states she cannot have a cat or any pets and now the landlord says it was mentioned verbally. Is this even legal? The landlord had no idea that my friend had a cat cause she never mentioned it. But somehow had an eviction notice on her door stating no cats allowed and that this was her 24 notice to enter her apartment. She also said her bathroom door was shut and she never shuts it as her cats food and water was in there so in other landlord entered without permission but no way to prove it