Your team should have told her is was a problem the first time. I get that airline employees are facing trying times - but you cannot have your staff flip flop like this. It makes it impossible for us to follow your rules! Happy Holidays!
@AmericanAir Your team at LGA is currently making my sister’s Holiday travel a nightmare. She is using the same carrier your airline has previously accepted to travel with her dog (ticket purchased). Now your team is telling her it is too small and she cannot travel with him.