UPS is being UPS here.
They're abandoning packages, then sending her a bill for COD as if she accepted the package but didn't pay.
The fact that if she digs in and fights it she can eventually dispute each charge is somewhat separate from UPS and their collections contractors harassing her about the 'debt', or the new packages that keep showing up.
I still go back regularly, but after grinding out pretty much everything - there's not really much left to do.