Your point about having form letters furthers my initial point that it is only as difficult as knowing the regulations and putting systems in place to ensure you're in full compliance.

I'm not entirely sure what the problem is.You brought her into compliance with the request for pets forms which is great.

Changes to the rental agreement must be done in compliance with the landlord-tenant law for your jurisdiction.

Do what's necessary to be in compliance with the landlord-tenant law for your jurisdiction.

Many iof these compliance liens are super-priority and run with taxing authority.

Be sure you do some research on your deductions before you complete it and make sure you are in compliance with 704 and 134 in Wisconsin law.It seems you may be inexperienced in being a landlord, I recommend you join a local landlord association and start taking advantage of any classes or training they offer.

Due to my previous compliance life, I agree that standards/policy and disclosure are keys to staying out of trouble.  

If they start digging I am already in compliance.

Do you have any tenant non-compliance clauses in your lease that would allow you to fine the tenant for violating the pet clause?

You may be able to document an increase in premium by your carrier, or if they drop you for non-compliance to their banned breeds list and you have to find a different carrier with additional cost, and turn that into "financial burden and hardship" as the reason to not accept an ESA.