My best advice is to do two things.
ONE-Pray to tbe blessed mother that your wife will have a greater devotion to her. A good devotion is the devotion of the first five Saturdays. Check the post on favorite Marian devotion to see my reply to that and you can get it.
TWO-Give her some literature on Mary and why she’s so important. The first place I would go is a parish library. If your parish or a parish near you has a library, I’d say go for it. Try to find something that would answer questions to non-Catholics, even though your wife isn’t a non-Catholic, I’d assume from what you said, that she has a non-Catholic view on Mary. You could also go to
www.biblechristiansociety.com, or you could go to
www.catholicity.com to order tapes and cds on Mary. Also, you could check your local Catholic bookstore. If you don’t have a Catholic bookstore, then the place I would go to is just a regular bookstore like Barnes and Noble, or Borders. They should have something, plus, you get to keep the book.
Also, check the Catholic Answers Online store. They have some very good books on Mary.
But one of the best things you could do is show teachings on Mary in scripture and in the Catechism. Also, if you could, get your hands on some of the writings of the early church fathers that deal with Mary.
Hope this helps!