Question ..missed the first ten mins of movie

She cut herself during her birthday and then a raven pecked at the wound, infecting her.

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Resistance is impolite, Friendship is mandatory.

Actually I believe she was born as the antichrist and it didn't take hold or come into effect until the bird incident. It was just time for it to be revealed. They mentioned something near the end when they were going to do the exorcism about all the signs and the timing of it.