Marceline has new morals and a fresh view on herself and others, and through the rest of the series we see her grow more and more after this point. She’s accepted being a vampire forever, most likely never dying, she’s okay with it. She also has more empathy and understanding than before stakes takes place, especially with those she views as “just bad”, “needs to die”, as shown with the vampire king after their conversation in the sky.
After stakes Marceline is more “adult” than before, and she’s “softer” less hellbent on rage and “punk rock energy” you know?
She lives as both her vampire self and her new, matured, empathetic, self. This mini-series is nowhere near the end of her or anyone else’s story but it’s my favorite part of their stories.