She actually likes the People Widget showing the published profile picture of the sender of each message; it's just its new "feature" of showing photos that were attached to an unrelated e-mail, that she doesn't like.  She would prefer to disable this unwanted "feature" without completely disabling the people widget.

For a few hours after she deleted the message from Trash, she was still able to access it by clicking on one of the photos in the People Widget, which would then show them in the context of the message, including its text body.  This ended when I sent her a newer message with different photos attached; they replaced the others in the People Widget, and hence her access to the deleted message.