I would take along a few patterns that I know I could make easily, and let her choose from those.
I made the mistake with my DDIL of letting her go through all my magazines to choose the one she wanted for her birthday. The very last magazine had an argyle quilt she just had to have.... About a zillion offset seams that I had to master! lol!!! The frustration was killing me for quite awhile, took the fun right out of it. (DH was also having surgery, etc, and I had no focus) But I did master them, and ended up liking working on it towards the end! :)