Isn't she just a bit foolish? If elves live as long as 10000 years, her father can keep ruling for the next 100 years and she can live her life with the MC and then come back once he has passed away, become the queen and remarry with a suitable partner. Although the elves might find it shameful that her first partner is a human, the king made that human a noble with a rank befitting a high elf, so there's no really issue.