I'm of the mindset that he can set boundaries for himself but his wife gets to set her own. I don't know for sure how their marriage is in general, but I know that my husband, for example, does have a similar situation to a T - there are boundaries and whatnot. If I'm going to send a friend request to someone or if I'm going to do something that relates to his job in a more social situation, I talk with him first.

Basically, it's likely she had a conversation with him before sending the friend request. Not a guarantee, but a strong possibility.