It wasn't that Bai Jingfei wanted to go to war to defend her country or some other bullcrap on a higher moral ground.
This wasn't even her country, she hadn't even been here for a week. And on top of that, this wasn't even her world if we wanted to get real formal about it. And even if she had been in her original world, it was unlikely that she would ever fighter for it.
If she had to die, she had to die. Why would Bai Jingfei want to struggle?
Her life had always been relaxed and fun. Why would she ever want to go out struggling for her life, or someone else's? They were all going to die anyway… There was no reason not to enjoy yourself.
She had never once thought that she would have to struggle for something, whether it was something useful or not. She had no fear of death either, made apparent by the many times that she had blown herself up without any hesitation for her life.