service animals of a tenant's guest

[Mike R.]

Still trying to understand what we have to do to accommodate a service animal, but long story short, we have a tenant  (the only person listed on the lease) that we have noticed the smell of dog and cat when our lease specifically forbids animals.  when asked about the smell of animals, we were told that the significant other (not listed on the lease) has a service dog.  we explained  that pets are not allowed and that they are responsible for their guests to which she responded that we have to make accommodations for that dog.  

so a few questions:

1) we don't believe we have to make accommodations for a supposed service dog a non-tenant.  are we correct?

2) the damage to the unit (i.e. the smell) is from the carpet which was relatively new when the tenant moved in and did not have an oder.  we believe we can deduct the cost of new carpet from the security deposit because it isn't normal wear and tear because the lease prohibits animals.  are we correct?

3) we actually know someone who wanted to bring their dog shopping and to restaurants, so they asked their Dr. to write a letter saying the "needed" the dog (i.e. it was a service animal) so i doubt this is really a service animal, but can we ask for proof that the dog is in fact a service animal?