Unfortunately no, nothing can be done to fix cracked canvas. You can try taking it in and hopefully LV will give you a credit for the cost of your bag. It's an older bag though so they might not. I'm sorry this has happened to your wife's bag.
From what Ive read on the forums LV doesnt do any repair on cracked canvas material. I would definitely bring it to the store and try talking to them. I dont think this is normal wear and tear on a 3.5 year old bag. For that price I would expect it to last longer. Was it purchased brand new or preowned?