Meeting in hotels-- who pays?

I've been in a similar situation. This is a rather ambiguous situation where everyone is entitled to their own opinion. So I think they just need to talk honestly and find a solution that suits them both.
Hi all,

I am just seeking some advice on my situation. My wife's regular generally meets up with her in a hotel room for the night, which he pays for.

It’s his birthday coming up and they have decided to go spend the night in a hotel room, like they always do. However, because it was a last minute idea and it’s his birthday she feels like she should pay for all/half the room. This would be okay, but at the start of it all she said she would never pay for rooms and let him sort it out. Being single, he's more financially able to afford it, as opposed to her having four kids to deal with.

I'm kind of thinking of letting her decide what she wants to do, but am I wrong in questioning this? Thanks.
This seems simple to me. If she can afford it and it’s his birthday, and you two agree then let her pick up the tab. It’s about communication.

Just like sex, if consenting adults are communicating, and all agree, there’s no right or wrong.
Just a note that this is a 3-year old thread and the OP hasn't been here since March 2021.