netmeg - 3:00 pm on Aug 4, 2011 (gmt 0)
As I just got finished saying in the WP forum, every site I've thus far put into WordPress (both for myself and for clients - maybe 25-30 sites) is doing better traffic-wise, earnings-wise and maintenance-wise than it was before. But it wasn't necessarily immediate - some took a few months.
If the site is doing pretty well now, I don't know why you'd need to change it. It's true that Google does pick up new WordPress posts pretty quickly - my record is about three minutes after I hit "publish" - but if the existing site is spidered pretty frequently, it should get that content quickly too. I have ecommerce sites that pick up new products in 24 hours.
One thing you might try, just as a lark, is next time she adds something to the static site, put a date on it. See if that gets it indexed faster. (You can always remove the date later)