Traci,
One thing to consider is that she will be the very minimum age the CM recommends for oral narrations. So, she’ll be new at it, and narrating is a skill that builds upon itself over time. I wouldn’t worry too much if she misses a few things or can’t seem to come up with much at times. You should find that her narrations will start very small, but that over the year or two; they should be getting longer.
Also, not all books are as easy to narrate from as others. You may discover that after you ask for narrations for a few weeks; you can get better narrations from some books and not so great from others. My 8 1/2 yr old is this way. She draws a blank when asked to narrate from the Bible sometimes, but when it comes to Burgesses Bird Book; she can give you back nearly verbatim what you have read.
Another thing I want to mention is to keep the selections read very short. Especially for a 6 yr old just beginning, I wouldn’t expect them to narrate from more than a paragraph to a page at a time. I could be wrong on this, but that has been my experience.
Hope I’ve helped.