Alex can't tell her boyfriend that she's a private detective?
Aside from the martial arts and various disguises / outfits or whatever silliness is on the screen, these three women are basically detectives. She's not a top secret government spy like Valerie Plame, she's not a superhero like Batman, she doesn't wear a mask, she never goes under an alias or nickname.
Furthermore, Charlie never expressly forbids her from revealing her job to her loved ones. Both Dylan and Natalie's boyfriends know.
In the sequel, we find that Alex still hasn't told her dad, either.
I keep trying to imagine other fictional detectives hiding their identity. Imagine if Detective Olivia Benson from Law & Order felt that she couldn't tell anyone that she was a detective. Weird.
Easily the most nonsensical part of this movie.