بسم الله الرحمن الرحيم
Ask your sister to recite Ayatul Kursi and four Quls before going to bed and blow on her hands and pass her hands over her whole body. Also, ask her to recite tasbih Fatimah before sleeping. She should also recite the following dua five hundred times in one meeting or several meetings with wudhu:
حَسْبُنَا اللّهُ وَنِعْمَ الْوَكِيلُ [آل عمران : 173]
In-sha-Allah, gradually the chain of bad dreams shall come to an end and she would get rid of unpleasant incidents.
Allah knows Best!
Darul Uloom Deoband