The parents expected the costs to be split equally once more, but the author and her husband refused to fund the girl’s accommodation
This year was no exception, and the OP and her friends decided to go to Fort Myers, near Sanibel Island in Florida. And when the friends were going to book a rental, a problem arose… The thing is that one of the couples decided to take their 12-year-old daughter with them, a big fan of seashells, which this place is famous for.
Yes, the OP’s spouse fully supported her in this dispute. The third couple hesitated, but then offered this time to split the bill – just to ‘to keep the peace’ – but only this time, nothing more.
As for the financial aspect of the described situation, here the majority of commenters unequivocally sided with the OP and her husband. Firstly, according to people in the comments, it is not worth creating such a precedent at all – so as not to tempt these parents to do this again in the future. Secondly, no matter how friendly the couple are with the girl’s parents, this is not a reason to de facto pay for her accomodation.