Of course you are creative. If you weren't you would be dead. It is your human heritage to be born creative, if you weren't you would not have been able to maneuver the day to day tasks needed to travel down your life's path. Your sister is creative, in her way. You are creative in your way. Comparing your self to her is like Picasso lamenting he wasn't creative like Rembrandt. We need all visions, yours is just as wonderful as anyone else's. Never tear down your own inspiration by comparisons with others. Be what you can only be, uniquely your self, only you can make a quilt in that way even if you follow a pattern or use a kit with fabric provided. If you draw inspiration from a source, don't feel guilty just remember this, All artist borrow, great artists steal. Someone very creative said that, I can't remember who exactly but it is true. We stand on the shoulders of the artists who came before us. Picasso would not have painted as he did if he had not been inspired by the way Rembrandt used light. Now aren't you tired of beating your self up? So stop already.