Question (Spoiler)

I just saw the movie last night and my theory on that was that she gave too much info to the uninitiated man, Luke, including sharing what kind of creature it was -- a jötunn (the bastard child of the Norse god of mischief, Loki) -- which also may or may not have been it's name. Remember she told Luke that they had to willingly worship the jötunn in order to attain nigh immortality (elongated life, whatever) and they were forbidden to speak its name. I think that's why it slew her.

I just assumed that it was because she looked up at it when she was bowing down to pray which would explain why it removed her eyes. There's plenty of myths and legends about turning to stone or being set on fire when looking the monster in the eye.

I just watched this last night (post is old) - but I'd agree with the below answers that she revealed too much info to Luke, and/or "looked" at the thing along with uttering its name - obviously a no go with its rules.

But her story (correct me if im wrong) is probably more horrific. I believe that she was Anna Erickson, the wallet that was found with the expired 1984 driving license, along with a picture of her husband and two children. Most likely the family that owned the VW Winnebago. If we are to assume that groups of 4 enter these woods; two are picked off by hunting, one is marked for cult duties and eternal life, the other marked for sacrifice. I can only imagine that her kids were probably picked off first, and her husband marked for sacrifice (as she had the chest marking). What must her story be, assuming the "chosen" have incredible pain and suffering/guilt?