My condolances on the loss of your Dear Sister. I lost both of my sisters a year ago, within 3 days of each other, so I have some idea how you are feeling. If I were you, I would put this particular quilt away for a while, and start something else with bright, happy colors. Sense you were working on this quilt when your sister passed, it may be bringing back sad memories. As time goes on, you will heal, and can get back to it. Or maybe it will just remain forever a UFO. I hope you have many fond memories of your time with your sister.
Phyllis