well like Gustergirl said,a muzzle might help with her to learn not to attack cats,and she wouldnt be able to bite them or anything,but i dont know if i would want to do that.A behaviorist is what i would highly recommend.
i dont have any more help for you,and she does look like some Border Collie,so that might be the cause of her nipping,but i would hire a behavorist/