lucid dreaming is normally induced through nightmares, when you get frightened ina dream, you become lucid. Telling her that when she realises this is s dream, do not try to wake up, instezd try to realise that it is only a dream, and tell her to try something outragous and lighthearted in it, no matter how terrified she may be.

That should help her overcome her fear, but i am only a amateur so i cannot say much more on the subject.

I hope she does overcome this.