She is a pitbull through and through. That intense concentration on killing the toy is always going to be strong with her.
I think instead of reinforcing her natural drive to kill and shred and tug on a rope toy, put her energy towards retrieving or other doggy stuff, (even though she may not give a rats arse if you throw something and expect her to retrieve it.)
I believe if she uses her energy in other activities daily, and it's made explicitly clear about the attitude of a pit bull, she would be able to be rehomed with an experienced and willing pit owner.