First of all, my condolences on the loss of your sister.
I think most people are not even aware what causes them to feel like crawling into a dark closet and pulling the door shut behind them or what causes their bursts of enthusiasm, energy and creativity. Life is all "ups and downs", at least it is for me. When I finish a quilt or quilt top that I've been working on for months, I have a bad case of the blahs, not knowing what to do with myself. My case of the blahs spreads out and touches everything and everyone; at the same time, I know very well that I've been there, done that before and I will snap out of it before I do myself or someone else an injury. (In the meantime, I worry about absolutely everything!)
I'm no kind of a therapist, but I think the kindest thing you can do for yourself is NOT worry about that quilt; if you don't work on it now, it will wait for you. Ditto on starting another one ... if you don't feel the urge, don't do it.
To answer your question, how long does it take me to finish a quilt, either months or years ... usually years. My theory is that my UFO's and WIP's are not going to go bad, start stinking, and have to be thrown out. They just wait patiently for me.