Well...can she execute hit and run tactics?
Probably, because Vader is a tank and he's not the sort of guy you can afford to leave yourself open to. He really can't afford to take much attention off dear old granddad, leaving hit and run a viable choice.
Can she control the environment?
Unless it's a flat, featureless plane, yes. Anything else helps. In a forest, she'd drop a tree on him in like fashion. In an urban environment, she'd drop a ceiling or a lamppost on him. In short, debris is going on a date with his head in quantity. If it's there in the first place.
Can she give her two shorter weapons an advantage? Sure. And if she can't, she's still got her purple full length blade. Among other things, Vader's still throwing everything he's got at his grandson, and Caedus can't afford to take it lightly. It must be remembered that Vader did manage to work with a very young Mara as Emperor's Hand, back in the day, so she has a pretty good idea of what her father in law can do.
And yet, turning away from Mara's likely to get him shanked by assassin tactics. If it were D&D, you could picture flanking+sneak attack to get an idea of what's happening to Caedus.
Rage amp? Probably the least important part of her arsenal. Besides, Vader has rage enough for two. (Even if he's mostly angry at himself, usually)