Is the trackpad in the Mac Air connected to the keyboard?
I'm sorry to hear about your wife's MacBook Air; it's always frustrating when accidents like that happen. According to this step in iFixit's teardown of the 2013 Air, it appears that the trackpad is attached to the motherboard, instead of the keyboard:



Again, best of luck with the repair of the MacBook. If she can do without for a little while, waiting for a refresh in the line may be worthwhile, depending on the extent of water damage that isn't readily apparent (water damage can manifest weeks or even months after the fact.)