Gee, isn't life full of learning experiences. I have been in a few similar situations when sewing for hire over the past 35 years and have tried many ways of dealing with customers/friends. Been there... been the doormat, been resentful about it. Thank God for maturity and the truth. That is where I would begin, with the truth. Calmly, directly, with only as many words as it takes (no rambling, no whining, no detours, highlights only) tell her your feelings (or read it as others suggested) about how this quilting "adventure" has played out and that you are no longer interested in participating. Sure, it may cause a rift. But if she is really your friend and you have dealt with her in truth and love, she may go home and think it over and come away with a greater respect for you. If she never speaks to you again, at least you have been true to yourself and gained a new skill of communicating directly in an awkward situation.