It will probably be fine, but it depends on what the material is on top of your subfloor (the underlayment). Subfloors are generally solid wood planks or sheets of outdoor treated lumber and your surface flooring can generally withstand quite bit, but sometimes the layer between the two is made of fairly cheap particle board. If this gets wet, it will begin to swell and it will stay wet enough to rot both itself and the subfloor away. The easiest way to check this is if you have carpeting anywhere in your house, look beneath it. If its particle board, your wife's worries may be well founded.
I had this happen years ago when my refrigerator ice maker tubing broke and I came to home to water everywhere. I dried it all up and it looked as if everything would be fine, but what I didn't know is that who ever built the kitchen put particle board in beneath the surface floor and the subfloor. Some weeks/months later we started noticing a hump in the floor. Eventually it was like walking on waves. When the contractor who remodeled my house eventually took everything out, that particle board was more less wet dust.
Another piece of information I didn't know at the time was that I could have had to whole thing paid for by home insurance which covers burst pipes. Recently when I setup my large system, I want to make sure I got coverage for a catastrophic event involving 300 gallons of water in my house. What I found out was that I was already covered because they look at aquariums as just another type of plumbing. Your mileage may vary.