I think you got it wrong? It's said here that she caused them to die, not see them die, which could mean that she already knew that they are next after her which also doesn't explain anything.There's a possible 2nd explanation which is more reasonable but I haven't read the novel so idk.Tbh I'm not so sure but based on the 1st part you shared, she can see them so the 2nd part should be something like her soul still haven't left so she saw them die one by one??Not sure but I maybe this would be explained in the story later slowly.
