Service animal question

[Crystal Hoover]

Hi, I have a question about service animals. I have a short term furnished apartment I rent out and I have a tenant inquiring about it who has 2 dogs.

The space is very small so I only allow small dogs or cats. She has 1 small and one pit bull (for size reference, not breed shaming). She says “the pit bull is a service animal but was her sons who is now 18 so she has the dog”. I know I’m not legally allowed to deny rentals to someone with a service animal and it’s not my business why the son doesn’t still need the dog suddenly after turning 18. But is it legal for me to deny renting to her because the dog is not for HER disability. I’m under the impression that the law pertains only to those with the disability (which I’m happy to accommodate for), not for the animal itself. Thanks!