Navigo Decouverte or Paris Visite?

Question

my aunt is going to Paris arriving on Wednesday and leaving Sunday (so 4 days). She wants unlimited number of rides. She will be only in Paris (2 zone?), except for the airport CDG. Which is best for her?

She said there's also a Roissy bus to and from airport. Is Navigo Decouverte with zone covering the CDG airport cheaper, or Navigo Decouverte zone 2 + Roissy bus cheaper? (how much is Roissy bus from CDG?)

And what about the Paris Visite?

Anyone in Paris or recently there? (the Navigo Decouverte is a new thing)