MEN: Would you tell a girl if her fly was unzipped?

I was at Dunkin Donuts the other day and noticed the girl making coffee/taking orders left her fly down. When I got up to the counter I told her. She didn’t understand at first and I had to say it again. It was pretty awkward when she realized what I was telling her. I got my coffee and left as fast as I could.

Should I have told her? She didn’t seem happy about it. Maybe it was embarrassment?