(In case it was not clear: She’s simply scraping the bad berries off the old pie and filling it back with new berries, reusing the pie crust.)
Disclaimer: This is only a speculation. She may as well be supplying them to the bounders as a bio weapon against the Dourhands for all I know.
Seriously though, WHY does she insist that we deliver all of them back to her? It can’t be to save her reputation, because I already tell them “Holly gave you a death pie, so please return it” before picking them up anyway.