Renesmee Cullen had practically everything a girl could want. She had a loving family, all the money she could ever need, looks, smarts, a handsome and funny boyfriend. There was just one small, well, ok, it wasn't small. There was just one big problem with her life.
And that problem's name was Leah Clearwater.
Leah had run away after Renesmee had grown old enough for Jacob to love her. And love her he did. He lavished her with hand-made gifts, was always there when she needed him, and could always make her laugh, even when she wanted to cry. Jacob had been only slightly concerned when Leah ran away.
Then she came back looking very pregnant. She had run away 8 and a half months after Renesmee's "18th" birthday. Renesmee had no idea that Jacob and Leah had had a fling. She flew into a jealous rage when Leah came back, threatening to kill her and that stupid..thing! they called a baby.
Jacob sided with Leah.
That hurt, more than the fact that he had gotten her pregnant to begin with, more than the fact that the baby was half his, and because of that, she couldn't kill Leah and the baby, as it would hurt him. Jacob had sided with his Beta over his imprint. That had to be a werewolf first.
Jacob told Renesmee that she would be a great stepmom, that she could play with his and Leah's daughter (and it was a girl. They had Carlisle check.), and that she would be able to love and cherish that little girl with all her heart.
Renesmee told him to go to hell.
He went to Leah instead.
That was the first time Renesmee Cullen was truly jealous.