This is an unusual situation. I wish I had more information. It is possible and very likely that the stress of her father dying is contributing to the paranoia.
You can try speaking to your friend about the importance of focusing on reality. For instance, she believes these things are real but does she have proof? In all likelihood, there is no proof. Pointing that out to her might help her to see reality more clearly.
You can also suggest that they install cameras and/or a security system in their home. It might quell their fears or perhaps not. They might simply think that the security company is part of the conspiracy.
You should suggest that she and her family seek help from a mental health professional. Your friend’s primary care physician can provide referrals to local agencies.
Do what you can but keep in mind that your attempts at helping may be ineffective. You can make suggestions and try to offer your assistance but they may not want your help. Also, it is possible that because of your efforts to help them, they will come to believe that you too have become part of the conspiracy.
I’m sorry that I don’t have a more actionable plan for you but it’s difficult for me to help when I have so little information about this unusual circumstance. If you would like to write back and provide more information, I may be able to be of better assistance. Thank you for your question. Please take care.
Dr. Kristina Randle