It's strange that Peter who is somewhat like a sponge could heal the power draining cut done by Sylar in .07% but Claire couldn't. She just stood there and apparently died.
When Sylar is killing Claire, it's clear from the movement of his finger that he is first cutting from her right ear to the left. But the blood is coming from above her left eye.
Reply, Sylar was attacked and Peter had the time to heal, Claire had no such time.