He is in the wrong here. If he offered to host a birthday gathering for his girl and he knew her friends were coming he should expect to pay. The exception is if they are all married/in relationships and bringing their men with them. Don’t offer to host and not pay. I am sure his girlfriend told him ahead of time her girls were coming. Believe it or not, the ladies saying “you are the man at the table” are correct on this.
Now, IF they showed up and he had no idea any of them were coming that is different. Highly doubt that was the case with a party of that size.
EDIT: The birthday girl is not his wife? Now this is confusing. If he is a participant and not the host, it is not on him to pay. He should have respectfully declined to show up. Why is he out on a dinner party with all women? Let your girl be with her friends.
That is my take. If someone can clarify the facts.
If you host, you as the man pay. If just participating, decline and let your girl be with her friends. Either way he fvcked this up.