Betty Grof

Betty was a human woman revealed to be a former fiance of a man named Simon Patrikov who would later become the Ice King. She and Simon used to have a very committed relationship until the Ice Crown was found and slowly began to corrupt the mind of Simon. Apparently when Simon put on the crown for the first time, something he did during his time wearing it until he finally took it off made Betty break up with him.

Trivia

 * Simon referred to Betty as his princess.
 * It is unknown why Betty left him, but it has something to do with what Simon did the first time he wore the crown.
 * Betty seems to bare a slight resemblance to Doctor Princess.
 * It is worth noting that in the prerelease publication, Princess Bubblegum's first name was Betty (it was changed to Bonnibel in the series.) However, it appears impossible that she is the Ice King's Betty, as she is 18 and the Ice King's relationship with Betty took place before the Mushroom War. It is worth noting that Betty in the picture on the Ice King's tale is wearing a lab coat, which means she might be a scientist like Bubblegum furthering the resembalance between the two.
 * Betty may have left him due to his side-effect on the crown.
 * Ice King's crown may have been nuclearized before Simon put it on.
 * Betty could possibly be PB's mother or grandmother or great great grandmother because of such resemblences with Betty and PB.