Actually 3 endings for Estelle:
Whore: You failed to ally with the tribes in Estelle's kingdom so she had no choice but to "marry" to those tribe leaders to stablize the kingdom(or become a playtoy more precisely).
Assistant: You helped her to ally with those tribes, but Estelle doesn't like you enough, but she still keeps you around her as a royal assistant.
Marriage: You helped her to stablize the kingdom, and she liked you and married to you. ONLY in this occasion you can unlock sex scenes with her.