I can see a whole load of potential problems with buying a dog from your T.
From her perspective it is potentially dodgy ethically, but also it could end badly for you. This puppy would always be emotionally linked to your T. What if you have a huge rupture? Will you want to take care of the puppy if you are angry with T? What about if you leave therapy, will having this dog make it harder for you to move on? What if the puppy gets sick or has a hereditary illness? Do you want to end up in a dispute with your T if you are suddenly lumped with heavy vets bills?
It just sounds like a potential minefield that could disrupt therapy for you. If you are currently in an apartment, why don't you wait till its more practically viable then look for a puppy from an independent breeder without the emotional baggage.