Since everyone seems to be confused on how I Surrender ended, here are answers to some of the questions I've been getting lately.
Why can't Dandy be with Ponyboy?
Dandy can't be with Pony because she feels like she would be betraying Darry. After all this hard work he's done for her to make sure she's well taken care of, and then he sees Dandy with Ponyboy, he'd think the only reason she wanted to spend so much time with the Curtis family was so she could have bae time with Ponyboy. That could turn into a disaster.
Why did Dandy kill herself?
Dandy had serious anxiety and post-traumatic stress disorder after Dally's death, and this is mentioned in one of the chapters of I Surrender. After all of the stress and guilt coming from dating Ponyboy, it was just too much for her to handle.