How about creating two custom columns, one for you and one for your wife, to show what has been read or not read. Most people use "Read" for the column name and the yes/no format. I took a reverse approach and labeled my custom column as Unread and used the rating format; one star equals unread and no stars means its been read.I find it easier to see what's been read or not at a glance that way without having to do a column sort to separate the yesses from the noes (I had to look up the preferred plural form of no!).
XP Pro SP3, IE 8