You know, this pattern, Radiant Star, is not the easiest for a beginner to do, and for a variety of reasons. If I were you, I'd make one for myself first so you know what you are getting into.
Here are my thoughts:
1) You are having technical difficulties now on one of your own projects. It will be worse later when combined with the stress of a project for another. These current difficulties, IMHO, should be well past you before taking on a commissioned project.
2) You are still learning. As a teacher, I would suggest you get some easy quilts under your belt first.
3) I don't know how much free motion work you have ever done, but for most people it takes about a hundred hours of practice before they feel they have begun to understand the process.
I would humbly suggest that you try something easier to start, like a log cabin. Since it would be a learning experience, and this is a good friend, let her buy the supplies, and you supply the labor for free on a pattern of YOUR choice.
Just my 2 cents...your mileage may vary.