Don't spend money and time to file I-90 yet.

If your wife just got her interview in this past Sep. then she might need to wait for more than 3-4 months to get her green card because it takes time to make the card. If she still doesn't get the card after 6 months, then she can go to CIS to fill out a special form requesting the status of her card. Also when you move, don't forget to notify the CIS by filling out the CHANGE OF ADDRESS form.