I think I can definitely help with this one.First off,reassure your friend that there is no hidden urge to do anything to her children,the images in dreams are just that-images-with meanings that rarely can be taken literally.
When a child is molested,the harm goes so deep,it may never all come out.Anytime we dream of our own children,it is the innocence of our own youth that it represents.If I were to dream of my son,it would mean my own childhood,and how much of a tomboy I used to be(and still am).Because your friend was molested,it is her own experience that she is reliving,in her dreams,only with her childs face in her place,because her child represents her youth.Her own face becomes the face of the molester,in the dream,because it would be too much for her mind to bear,to put the real molesters face in front of her,so to speak.
Basically,her subconscious is trying to deal with the continuing pain that she feels being a survivor of such a horrendous act.This happens to many survivors,and she is most definitely NOT alone.I have heard of rape survivors(I hate the word "victim")who would dream ,for years of being raped by animals,usually either apes,or wild dogs,or of raping soming else.Survivors of beatings sometimes dream of beating someone to death.So please assure her that what's happening to her is in no way abnormal.
She is very lucky to have a friend like you who she feels confident enough to confide in.Please let her know that the more she lets herself open up about it,the easier it will be for her subconscious to come to grips with it,too.