um... her j.C outranges your j.C (and it's active forever), so i would recommend never being at the same vertical height as her. Stay above or below her in teh air so you can abuse your j.B to hit her where she can't easily hit you.
as for avoiding steins, they lock onto your position when they are deployed, not when they actually shoot. so jump, double jump, land, run in (but don't run into her attacks). if she gets too stein happy, you can punish her with ice wave if you're smart about.