Correct me if I'm wrong, but isn't a retreat supposed to relax you? After reading all of the replies and trying to imagine myself in the offender's shoes, I've thought of another possible solution.
Take with you, a few sewing or quilting books (or a few light novels or whatever). If possible, take one you wouldn't mind letting her keep. When she starts badgering you to do her work, kindly tell her you NEED this time to focus on yourself and your own project. Apologize, if it makes you feel better, for not being able to focus on her and her chosen project. Then offer to let her borrow one of your books, to help her relax and pass the time. Perhaps everyone should arrive, armed with books or magazines. If she's simply lonely, this will allow her to be a part of the group, while learning the craft. If she's only looking for someone else to work for her, this will serve as a gentle but firm refusal.
I also still think someone should offer to tutor her privately, at a later date (for a fee).