Again, you miss some of the points…
there is no ignorance of the rules…the renter KNOWS the rule - no pets.
(You know your guest has a nut allergy). The renter is going to bring the cat anyway (You are going to serve the nuts anyway). I pointed out the renter should ask the landlord if it would be OK. (You should ask your guest if it is OK s/he can have nuts, giving him/her the opportunity to tell you s/he cannot eat them OR these nuts are OK, it is just THOSE nuts s/he is allergic to).
My comment to stay in school was to point out you need to develop your thinking process…you are indeed a “young thinker” - inexperienced, not thought through, and well…you get the idea.

Keep working on it!