I inherited 1/3 of mom's massive stash in 2003 (two of my sisters also quilt) and last summer while making stockings for the troops through Project Santa, was actually able to donate some her fabric to that cause. That was also very healing. I knew it was something that Mom would have done and would have wanted me to do. Yes, everytime I pull out one of Mom's fabrics it makes me miss her and we "talk" a while, but it also floods me with such warmth and fond memories. The 'tearing up' probably won't change even after you combine the stashes but you're right, it's part of the process. Your mother probably loved her stash as much as we do so just think of it as her love still being with you. Each time you use a piece of it you'll be passing some of your mother's love to whomever you give the quilt to and her love will live on.