I think that providing support for free version is somewhat unique, however it does make sense - the longer people use her software the more likely they purchase add-on or subscription.
That way she can hear about frequent needs of users who don't buy the thing when it lacks some essential feature, also could upsell existing extensions or the boxed version. Customers often have no idea of potential the software offers.
Simply it is support+marketing+sales number.
I suspect that approach wouldn't work nearly so well if the connection between the software you're selling and the money rolling in to their bank account wasn't quite so obvious. I probably wouldn't try such a generous free version of, say, wiki software or document management or backups - things that are way too easy to consider as "cost centres"...