Marceline left without confronting Kira. She already heard enough. Kira didn't love her. He just wanted her for revenge. That was also the reason why Kira agreed on helping her before.
The two of them were supposed to get their revenge against the werewolf clan. But now, the situation has changed. She was part of the werewolf clan. She is a werewolf princess. And the only werewolf whom she should blame for the death of her adoptive parents was Cedrick Morgan!
Once she got her revenge, Marceline had to help the Moon Goddess to reunite the creatures– werewolves, vampires, witches, humans, and hybrids! She must stop the war no matter what.
But she didn't know how she would do that. She was now heartbroken because of Kira. She didn't know if Kira had feelings for her or if he was still in love with her mother, Serena.