While I certainly agree with all the comments posted so far - here's a different perspective for you. Consider that your sister would not have been able to come up with the suggestions she did if you had not put the initial pieces together! I am sure you are very creative in your own right - just a different type of creativity than your sister's.
Also consider that many of us can not see errors (oops - meant to say design options) in our quilts until we are done and have photographed them - has happened to me more than once. And even then, some of still don't see that upside down block until someone else points it out!
I'm in the process of doing my first original design for a quilt after about 15 years of quilting. Can manage different fabric choices for other's patterns with no problems. This is not an 'artistic' type quilt in any way, shape or form. I've shown the progression of my design to any number of people, all of whom have had great suggestions as to how to get it closer to what is in my mind's eye. I am very grateful to them all. I'm almost ready to start slicing/dicing/sewing. Maybe a few more tweaks as I go along. We'll see.
Check out Quilt University if you are looking for some long distance/online classes. I believe they might have something that you might be looking for in terms of techniques, etc.
Continue working your design with or without your sister's suggestions. You'll know when it's what you want.
Good luck.