User blog comment:Zippertrain85/Dawnguard Follow up./@comment-17114085-20131216013719/@comment-17114085-20131220170036

Zip, there are three ways that can explain why she knows what a High King is and that Skyrim has one.

1) It was Harald who defeated Harkon and took over whatever part of Skyrim Harkon was controlling. Then Harkon and his family escaped to the castle, and Harald was proclaimed High King.

2) They heard of what a High King is from one of their servants, the human ones or the vampire ones. As obviously they would need to capture new humans to use as servants and to feed from, therefore they could hear about the High Kings.

3) She read it in a book, since she spent a lot of time in the castle then through one of the servants or whatever she came across a book that told of the High Kings. Evidence to back this is the fact that there are fairly recently published books found in Castle Volhikar.