I was actually thinking that. In 2 and 4 she was always the pro who focused on getting the job done over personal feelings. Though she's generally helpful to Leon and obviously does care about him, she has no problems using him to accomplish her own goals.
I never really thought she had any real problems with bioweapon development/use in general given who she was willing to work for. To an extent I understand what she did in 6 though, since Simmons and Carla started the ball rolling and from her perspective she was probably just cleaning up loose ends and protecting herself.
I don't know about 'too nice'. She always had her own agenda.