If your wife is anything like most of my friends with iPads, the problem is probably with the message she is sending. I frequently receive e-mails from i-Pad users, who've taken a photo and decided to send it to me. What arrives is an e-mail with no subject line, no signature, and simply the words "sent from my iPad", together with an attachment, usually called simply "photo.jpg".
It's pretty easy for this to be misidentified as spam, as a favourite trick of spammers is to send their messages as images, to try to thwart antispam engines that are looking for key words.