My Sisters Keeper ending

After I finished my sisters keeper i was shocked that Anna died. I'm happy that Kate lived but I don't think Anna should of died for that because Kate wanted to die in the first place. I was suprised when it said that Jesse became a police officer. It does not make sense that the author is making Kate live the rest of her life in guilt. I can not imagine how the mother feels about all this happening. I think there should have been a more happy ending to the story.