This whole story is nonsense. Maybe they will eventually turn them over, possible its just a way to delay and embarrass the congress. But I do not for a second believe that the IRS did not have mail servers and back-ups off-site, relying solely on her personal computer to save/store all communications.
More likely is a) intentional destruction, b) mischief brinksmanship/game playing between branches, c) she used a personal mail box to avoid the kind of scrutiny she now faces.
Right on. If an email left her computer or an email was received on her computer, it is stored somewhere.