It's not a problem at all. The ability to memorize a passage after a careful study of it is a blessing, and won't hinder her development as a writer at all. Later on, in our next book, we teach ways to shuffle sentences around, by means of paraphrase, synonyms, reordering elements, and the like. This is a little early for that.
Since she's got the content part of the narration down pat - at least for this model, and quite likely for others as you continue - you can turn your attention away from that to punctuation, capitalization, and other things. if she's got those memorized too, then the writing projects at this point may just plain be easy for her. If everything were easy, I'd suggest picking up the pace. Since you mention that the preparation/analysis was a challenge, I'd keep working at the same pace, and the difficult parts can be balanced by the ease of the narrations.