"We were hoping she would own-up to some of the things she did," Marshall told "Extra" in an exclusive interview.
Marshall, who grew up very close to her sister but has been estranged since Hunter moved to L.A. 16 years ago, thinks Hunter really hurt Edwards' wife, Elizabeth.
"They were married, she has cancer. She has two little children. She deserves some respect," Marshall said. "I would like to tell Mrs. Edwards that I feel so bad about the whole situation, and in my heart, I feel for her."
Marshall admits the entire family was "pretty upset" Rielle didn't apologize herself when Oprah gave her the chance.