Relax. You may just be trying too hard. You didn't say there was a time frame you had to work around. You can be honest and tell your sister you really love her idea and maybe you'll try it another time but you think you'd like to try this one on your own. Look around in nature while you're walking......let your mind wander...think about what makes you happy... I've found you just can't force an idea. But you WILL get one and when you get do, just jump in with both feet and don't doubt yourself. If you add something and you don't like it you can frog stitch like the rest of us....you know...rip it, rip it, rip it. LOL Happy sewing!