Things like this can manifest pretty late in life. My adopted brother has an ability, but it didn't become obvious until he was 16. Mine manifested at 5, but it was due to... an usually high amount of stress.

Which leads into the next question. Has something stressed her or worried her, recently? You mentioned headaches, but do you think anything could've triggered them, knowing this now?

As well, has she ever mentioned anything about her family? Sometimes things like this can be hereditary...