Spring Break is a hard time to find a good deal to warm destinations...
Have you looked at Vacation package deals?
Disclosure: I work for Alaska Air.
http://www.alaskaair.com/as/www2/pro...on-Savings.asp
You could book a trip together out of Seattle, then book her separate tickets from Chicago and she could spend a day or two in Seattle with you on each end of the trip.
Or you could book the vacation package for just yourself and then buy flight direct from Chicago to wherever you are going.
Puerto Vallarta? Cabo? Hawaii?