Ihsan Allahu Ilayk when my sister doesn’t do ayat al-Kursi or listen to Quran when sleeping she gets nightmares (may be sleep paralysis) and gets a headache when she awakens with a ringing sound. Is it possible that this could be sihr? Any advice?

My advice is that she makes wudu, sleeps upon purity and on her right side, and performs the following: 1. The adhkar of morning 2. The adhkar of night 3. The adhkar of sleeping 4. The adhkar of waking up There is a book called "The Muslim Fortress" that she can buy which will help her a lot, and it is also available online.