The thing with Syl actually bothered me, why did she "die" at the moment when Kal fell into the chasm? If it is about broken oaths, she should have died much earlier on.
Yet, when Kal charged to the broken bridge, in attempt to protect Dalinar, Kal is protecting; when Kal escorted Shallan through the chasm, Kal is protecting; when Kal tried to use himself as a decoy for Shallan to get away, that is noble sacrifice and protecting.
Why didn't Syl came back then?
Unless Syl's "dying" during the fall into the chasm is Syl using all her remaining strength, once depleted, then Syl "dies"