So I what do I do?

I was riven mid going full lethality had an executioners calling and I catch out the soraka, I got her to 200 hp before she reacted but then she ulted, ok whatever, and then she healed....And now shes full hp and now im chasing her down bot lane when she....Redemptions Qing and Eing the entire way my point is what the hell do I do when stuff like this happens how do I kill the support when they can heal themselves full 2 times over and build a frozen heart.