Mackenzie Shirilla's Father Says She Definitely Feels Remorse About Dominic Russo's Death

Steve Shirilla says his daughter, Mackenzie, definitely feels remorse for the way Dominic Russo died ... even though he maintains she didn't do it on purpose.

Shirilla spoke about his daughter's case on the "True Crime This Week" podcast in an episode published Wednesday ... and he says he sat with his daughter for months -- so he knows how terrible she feels about how Dom and their friend, Davion Flanagan, died.

Steve says Mackenzie had a shrine to Dominic in her room ... and he says she's repeatedly told him she didn't kill Dominic on purpose.

He also argues there's no way Mackenzie would've killed Dom the way she did if it were on purpose -- with Davion in the car ... saying it makes no sense to kill them both.

Mackenzie would've just shot Dominic, Steve maintains ... because Dominic already had so many guns lying around their house.

Steve ends the interview by saying he doesn't plan on ever giving up on his daughter ... continuing the fight for her release.

While Steve might think his daughter's full of remorse, Gypsy Rose Blanchard -- who served more than 8 years in prison in connection with her mother's murder -- disagrees ... saying she thinks Mackenzie's not remorseful at all and needs to get in touch with that side of herself if she ever hopes to get out of prison.