I am starting to lean that way. I wish I had a LBS near me.For something as important as a helmet the best deal on one is the one that fits best. There are only two brands of helmet that currently fit my head properly - and even if one of the other brands is free you would not get me wearing one of those.
*off soap box*
If you know the brand/model/size that fits your wife well chain reaction cycles also has a good selection of helmets.