In the forgiveness programs, interest is forgiven too. Private loans (from banks) are not part of the program. Paretnt Plus loans are not part of the program.
The woman in the original story should have been in a repayment status and then her payments (even if they were $0 per month based on a 10% income repayment plan) would have been counted toward a teacher loan forgiveness plan. I think some of her loans were from prior to 2007 so may not have been eligible (although they are now).
But she didn’t do that.