Saying "Doctor XYZ invested" as a way to lend credibility.

She says that the doctor suggest that she get a trained service dog. 

Registering a pet and a doctor's note may not be the same. 

Though I am training to become a doctor, I have a plan to use real estate as an investment vehicle that will free me from any bond I feel to work as a doctor because i need to do it to pay for my life and the associated expenses.

I interviewed a Doctor yesterday for a podcast...

The hope is it that if your tenants are spending less time at the doctor, more time at work, and spending less on utilities, they'll have more money for rent and will stick around longer.  

Private money lenders can be friends, family, your doctor, dentist, neighbor, people you know from work, from business, etc.

In our experience, once you agree to the deal, the doctor will ask via e:mail that you now deal directly with his "financier" (key word to look for), who will handle all the money and contract details from this point forward.

Now they tell me that they've registered the dog as a service dog, shown me papers, doctors note, etc.

Just like you have to complete undergrad before entering master and doctoral programs.