I'm clutching at straws a bit now, but if you can put her behaviour down to her health issues, perhaps you can stop blaming yourself. If she needs care, who is providing that? I know very little about narcolepsy, but who else lives at the house?
Careful who you speak to, as she may interpret other family members' or friends' intervention as harassment, but is there anyone in the family who is close to her? That may help you feel better just knowing that she has that person/those people for support.
Clearly her Dr can't discuss it with you, but make a list of why she may be behaving in this way. You may need it to defend yourself in case she takes offence at something you may say or do. Is she on meds for the anxiety? Has she taken an irrational dislike to others? Could it be medication which makes her this way?
It's going to be very hard and you are going to have to dig deep to find the courage to just keep coping, but your love will be your strength.
Nothing we can say will ease the worry, but yes, we're holding your hand from afar. Keep talking to us, we're listening. xx