I would get one of those mortein "bomb" things from the supermarket and get her really involved in ELIMINATING all insects and spiders from her house. She really needs this fear validated and worked through. Involve her in checking after the insecticide has done its thing. Then if the fear still continues I would invest in a mosquito net to put over her bed. They look pretty and really helped me relax when I was a kid...its like a safety net.

HTH