Landlord says we have too many therapy animals

Okay! Sooo, my landlord says we have too many "therapy animals". My mother got Sherbert (her 6yo cat) for my nephew but he has adopted my mom instead! My dog, Paco (13), is my "emotional support animal" & my mom's dog, Turbo (6), is her therapy animal. I reached out to my Psychiatrist & left her a message saying I need written documents stating that my dog, Paco, is for my Anxiety & Turbo for my depression. I'm hoping that this would work. Then my mother could just get her Dr to write out a letter for the cat!