I've read mostly the opposite. Where did you read that she remained a Nazi?
It's possible she lied, of course. You can't know what someone is thinking.
Frau Riefenstahl gave an interview when she was well into her nineties. She said that she found Hitler to be a nice man, and that neither she nor the Fuehrer knew anything about atrocities committed against the Jews.
“I did nothing wrong, Hitler did nothing wrong, Germany did nothing wrong.”
That mostly summed up Frau Riefenstahl’s attitude toward 1939-1945.