I believe the answer is simple. When sly says she is as dead as kaladin's oaths she means that she too can rise again if the circumstances change. I believe in the fall Syl chooses to sacrifice herself for Kaladin and in doing so she breaks an oath, she gives too much in their bond and she pays the price. I believe that when Kaladin hears the voice asking him what did you do, it is referring to Syl choosing to put more faith into Kaldin than she received. Syl invested Kaldin with the last force she had, her essence manifest in the physical realm. She created a conduit of power for him built of her own being, because she believes in his honor.
