My wife spilled a glass of wine on her MacBook Air. Now it's completely dead, and won't even show it's charging...

Liquids and electricity don't mix. Any hope of surviving a spill is based on immediately turning the device off, getting it as dry as possible, and then letting it have a lengthy drying period. Some people recommend putting it in rice to absorb moisture though I think that has its own danger. At this point your only solution is to take it to an Apple repair center and see what it will cost to replace the logic board - and to hope that was the only damage.

Sorry I couldn't provide better news. Check your home owners policy to see if this is covered (and if it is worth using). I have a specific rider on my policy for electronic equipment which includes full replacement value with no deductible.

dwb is right, there isn't much you can do at this point, the damage has already been done, and likely includes short circuiting at least the battery and logic board. All you can do is let the Apple techs, whether at an Apple store genius bar, or Authorized Service Provider, test the system and see what has failed and needs to be replaced.