I had a Chilean friend who had previously lived in the USA as a student, and then subsequently returned on an immigrant visa, with the intent of settling permanently in the USA. She had left her job in Chile, moved out of her flat, etc.

On arrival, CBP grilled her repeatedly about her previous life in the USA, demanding she admit that she had "worked" previously. They refused to accept her denials and insisted that she must have done "some" work. Finally, she acknowledged that she had done some volunteer work for her church, and that was it, bam!, visa cancelled, you are out of the country and not coming back.

The CBP loves to detain people and harass and intimidate them until they say something "incriminating". Make sure your wife understands to say as little as possible, and to never, ever be intimidated by these guys. They will undoubtedly try to get her to "admit" all kinds of stuff -- from bringing in undeclared gifts to being OBL's social secretary. If they decide to target her, they will try to make her believe that all she needs to do is just answer one question the way they want her to, and she'll be on her way. If this happens, she needs to stand her ground and not be pressured into saying anything, because if she does, the only place she'll be on her way is back home again.