Curate, connect, and discover
You know, I think Maki actually does feel guilty about Kokichi's death.
Yes, by Ch.5 she absolutely hated him, but it was understandable. He declared himself the mastermind — person who supposedly kidnapped forced everyone to kill each other. He took Kaito — the most important person for Maki in this game — hostage. He mocked Gonta after his death. He told everyone that he enjoyed their suffering, laughing like madman. Throughout all the game, he accused and insulted Maki of being an assassin. And finally, the last straw was the fake memories that he also helped Junko start wars and cause destruction. This all led to her snapping and trying to kill him.
And Maki never enjoyed killing. She was forced to become an assassin and only stayed for the safety and wellbeing of children in the orphanage she grew up in. She really wanted to prove the group. that she could be trusted. She even told this to Kokichi after the 3rd trial.
Yes, at the end of the fifth trial she told Kaito that he shouldn't have agreed to Kokichi's plan and it would have been better for Ouma to just die. But at that moment she was desperate, hurt and scared that Kaito would be executed. Naturally she would be mad at Kokichi.
But in Chapter 6, she was the one who volunteered to search Kokichi's room to find any clues that could help end the game. If she didn't care at all, she would not offer to search there. I think part of her also wanted to find some kind of confirmation that he really was an asshole who absolutely deserved to die. Or, on the contrary, confirmation that he really did try to help them. Just anything to form her own final opinion about him.
And also that moment during the Final Trial when Tsumugi, the real Mastermind, revealed that those memories, that finally pushed her to try to kill him, weren't real. Maki sounds shocked and horrified at that. Because those memories were the reason that pushed her to try to murder him. And if they were fake, that means she did all that for nothing. She broke her unspoken promise to Kaito, and that resulted in Momota and Ouma both dying. And all of it was because of a lie.
It feels to me that she does feel guilty for both Kaito's death and Kokichi's death, because it was her actions that partially led to everything ending that way. I think no matter how she feels about Kokichi, she regrets what she did.