If Video streaming is any indication:
1080p video streaming from a Bluray source can hit 45Mb/s peak on my PopCorn Hour.
That being said, I can easily watch a movie on my iPhone over 3G via Plex from the same source. Plex will transcode on the fly.
Does your Wife use Voice apps via Wi-Fi as well? Those would be the ones most affected. Web based text apps should degrade gracefully enough. Your Wi-Fi is N? on A or B/G ? Or are you worried about your Internet connection itself... ? In this case, what's your ISP provided bandwidth upstream?