Basically any place near one of the Metra stations on the Union Pacific North line, Milwaukee District North line, North Central Service, or the Union Pacific Northwest line.

http://metrarail.com/content/metra/e...ystem_map.html

I live near the Mount Prospect station on the UP NW line and I can get downtown in less than 40 minutes on one of the express trains. I don't know if the NW line would be good for your wife's commute to Northbrook. I can get to the Lake-Cook Rd exit on I-294 in 20-25 minutes in rush hour traffic.