My sister's nightmare

This happened two days ago, my sister and my mom were arguing fiercely again, my sister has been back-talking to my mother lately. Nightime came and my sister went to sleep, hours passed and my sister started to fidget and make loud noises in her sleep then my mom tried to wake her up, to which she opened her eyes and fiercely caught hold my mother's ankle and yelled "Am so sorry mom". My mom later told me that my sister had a nightmare of her getting buried in a dark grave, she then told me that it meant that my sister was going to go to hell if she didn't stop what she was doing. I was very confused about this 'cause i've thought of much worse things! What do you guys think about all this? 🤔🤔🤔