How do I fight Graves as Paradox?

I'm quite new to the game, so this is probably a pretty newbie question, but how do I fight Graves as Paradox? Even if I'm maxxed the hell out in late game, it feels like she can just outheal all my damage instantly, regardless of whether I'm building for weapon or ability damage. I wall swap her and then she leeches my health and is back to full hp in 2 seconds. How should I take those fights? Is there an item I should be using against her?