He was Jerusalem. (King Baldwin x OC fanfic)

At age 16, Aetri Bartlett dreamt that she was ahead of the frontlines, sword in hand and heading into battle.
So when Bartlet finds herself in 1179 Jerusalem, after dying a sudden death at the age of 17. She is shocked to find herself reincarnated as someone who just so happens to share the same first name.
Though when Bartlet discovers no proper historical evidence that this person truly existed, she is shocked when she recalls the one bit of literature she'd read just before her death:

Aetri of Blanche; a young noblewoman- the only woman- who fought beside Jerusalem's King, Baldwin the Leper, died at age 16 during the 12th-century crusade war in 1177.

Keyword: Died.

So her dream had actually happened?
But what is she doing inside the body of an already dead woman?
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.
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