When I was a receptionist, I opened everyone's mail, date stamped it, and delivered it. If someone was expecting something that they didn't want me to open then they'd let me know and I would keep an eye out for it. If they didn't give me a heads up, then it got opened. 

This lady has her personal mail sent to the office, protocol is for the receptionist to open the mail. If she doesn't want her mail being opened then she should, like Lynne said, get a post office box. I know some of the purchases may be gifts for her husband but since it seems to happen enough that she had to write to the newspaper about it, I'm going to guess she is probably being deceitful. 

All that being said, I bet this lady is an absolute joy to work with *need sarcasm font*. I'm glad the boss put her in her place at the retreat in front of everyone and now the entire office, if they didn't know before, knows what kind of person she is.