Why do girls cry when they're drunk?

I have a friend that used to be a fake drunk in high school. Well, she would really get drunk but she would pretend to drink all these beers. She would take the bottle/can, put it up to her mouth, do the head tilt thing and try to make it look like she was slamming a beer. Sure, it worked with cans but someone spotted the lack of bubbles in the beer and started making fun of her and then she started to cry.