This reminds me of a time back in college when a guy on the XC team was in the computer lab and one of the girls on the team was sitting right next to him. Using her log-in name (and not knowing the password) he clicked the "forgot password?" button and the secret question came up. He leaned over and asked her, "Hey, what's your brother's name?"
Well I don't know why she never put two and two together but lets just say many people on the team got some explicit e-mails. I still crack up laughing just thinking about it.
As for this situation, who's to say this chick didn't check the "remember password" box on her boyfriend's computer. My friend did it and she read his e-mails.
So if you are dumb enough to do something like this its your own fault.