Would you be okay with your current beau sleeping at his ex's house?

K’s boyfriend (H) is best friends with his ex’s brother. His friend introduced them and while the relationship didn’t work out, he gained attachment to his ex’s daughter, who was without a father figure. As a result, he sees them on occasion.

H went to a party at his ex’s with his friend. They apparently had a little too much to drink and he called K to inform her he wasn’t coming home tonite and would be sleeping there. I told her that at 45 years old a man should have the sense to have a plan to get home responsibly. She justified it by saying they spend a lot of time together and she was okay with it. I didn’t push beyond that- it’s not my place. It just seems weird to me, especially since she hasn’t met these friends. Am I old fashioned?