I have a young cousin who had a similar struggle. She ended up having to be institutionalized after trying to smother her sister. My cousin was only 7 at the time. She is now thriving in a facility and getting the help she needs.
Our sister needs to simply sit and talk to her priest.
The priest will work with this family to determine if there is a spiritual element. If the girl is baptized and this girl is living in friendship with God, this is likely a medical condition.
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