* Bella *becomes* a vampire at the end of Breaking Dawn. She doesn't live as a human in the end.
* However, she still exists as a vampire. So, in a way, she does live.
* The focus of the ending shifts to her daughter Renesmee. Bella's transformation and life as a vampire are essentially complete at that point, and the story focuses on Renesmee's development and the threat she faces.
So, to be precise:
* Bella doesn't live as a human in the end of Breaking Dawn.
* Bella lives as a vampire, but the movie doesn't focus on her life after the transformation.
It's a bit of a semantic distinction, but it's important to understand how Bella's character arc concludes in the movie.