recurring dreams

My sister is plagued by a dream. She has it every night. She can't sleep for fear.
Every night she dreams of a lady, he is an artist. It is very clear. She finds a book it is full of paintings, painings of mutilated bodyparts. The lady paints them. She is a murderer. This is horrible. Why is my sister's mind doing this to her? She has done nothing wrong. This is not fair.
The subconscious is crazy. I think about ti so much.. Who are we really underneath?
I want to make it better but I have to understand.
Aren't dreams menat to be a warning?

I only ever had one recurring dream... it was about wolves. I like having nightmares because they are exciting. But this is horrible. My dreams only recurr in themes.