I still think the most tragic part about Betty’s character is she might’ve actually been able to save Simon and stay together if she hadn’t jumped into the future. We know that he only became the Ice King because he kept wearing the crown despite what it was doing to him. And for a good chunk of time he was so devastated about losing her that he didn’t value his own life enough to resist putting it on again. When PB and Marceline go into the labyrinth they learn that some people (like Santa) had only put on the crown once, gone a little crazy, but still retained most of their sanity and lived relatively normal lives. Even after a few years of wearing the Crown (in Simon and Marcy), he’s still mostly there, and only goes crazy when he puts it on. It STILL takes another 4-5 years of him wearing it for him to decide he’s too far gone to be around Marceline without hurting her. If Betty had stayed she might’ve convinced him to get rid of the crown after he wore it the first time and prevented any further suffering- he would’ve lived with the condition in its most manageable form. They could’ve been okay. They could’ve been happy. Her love for him, her need to save him might’ve been the very thing that ruined him in the first place.
But then they might’ve just died in the Mushroom war if that happened. Without his Ice Powers he wouldn’t have been able to protect young Marcy or himself. None of them would have made it. Which presents a really fucked up paradox. They all survived in the current canon, but at the worst possible price. I’m SO excited to see what Fionna and Cake does with their characters I just know it’s going to have me sobbing in a heap on the floor