Don’t use all capital letters for emphasis; use italics.
When a new sentence begins after an ellipsis, capitalize the next word; when it’s still in the same sentence, don’t capitalize.
Use a comma before the conjunction in a compound sentence.
I’d change gotten up to stood up; it’s less vague.
Feeds off and devours are saying pretty much the same thing; unless there’s a reason for the repetition, get rid of one.
I’m treating You poor thing as a direct address, which is why I’ve added you after it. Another option would be to treat poor thing as renaming you — still a direct address — in which case no extra word is needed, just a comma: You, poor thing, won’t even know...
Have you ever stood up and your vision suddenly went black? It’s her. She’s temporarily blinding you… making sure you don’t see her. She’s stealing a memory… She devours them. You poor thing, you won’t even know what you lost, and you won’t even see her coming.