@SailorJerry - Tell your wife not to worry. (Or rather, you stop worrying. I've been there, my friend - two kids of my own. You're in for a real roller coaster!)
Vitamin C is a water-soluble vitamin. Your body can't store it like it can vitamins D and A, for instance. You can really poison yourself by taking too much D (though most people have too little vitamin D these days) or A because it just adds up in your body's fat.
On the other hand, if you take too much vitamin C, you get the runs. Which is bad enough for a pregnant woman, but it's highly unlikely that she would even get that far unless she were taking lots of pure vitamin C supplements. From dietary sources and her regular prenatal, she should be fine.