Bree didn't want anyone to die. She didn't want to die here in the world of a novel. She didn't want Levi to die for trying to do the right thing. She also didn't want Jasper to die even though it was his predestined end because he had been nice to her.
He wasn't a good person. She could acknowledge that the world at large would probably be better off without him. So why did she want him to live?
She was afraid of him. He was holding her hostage and could end her life at any time. She should want to be rescued, shouldn't she? Even if she didn't help the FBI, they were obligated to get her out if they knew she was here against her will, weren't they? She was the victim here!
The victim of a bizarre set of circumstances she could never explain to anyone without them thinking she was insane. No one would believe she had transmigrated into a novel like characters in a lot of the fantasy romance comics she liked to read.