But there are no "damages"; simply that Persia gets very, very upset when
this cat wanders up to the glass door or the windows or anywhere she can see
him/her.

Um, how about a white lie? How about saying the cats are spraying. Maybe they
are and just don't see them doing it anyway. Or maybe the cat is knocking over
pots, scratching your car by sitting on it...? Maybe it'll get her to be more
responsible.