do you have a couple beginner books around? i would allow her to choose a pattern & the fabrics- she may have very different tastes than you-
when my nephew's girl friend decided she wanted to make a quilt i cringed & shuddered over her choices- but she was liking them and completed the quilt---she was so proud of it--and she gave it to her grandmother as a special gift-who was thrilled- it was pink & brown & i hated everything about it- but it was not mine & i didn't have to work on it....had it been something i had to work on it never would have been done.
if you have a stash maybe she could (shop) your stash- then let her look through beginner patterns or pictures on the internet-
all 3 of my grandaughters made their first 2 or 3 quilts without patterns- they chose fabrics they liked-wanted to make into quilts- layed them out & made them the way they wanted- loved them-were very proud of them and were (hooked) on sewing. basically learning to stitch a straight line, cut & iron are the basics- from there--the sky is the limit & teens have such keen eyes & imaginations to be creative if given the opportunities.