This is how we are doing our quilts for the hospital..it works and it is easier for students and why waste fabric as you say, and as hard as it is, try not to waste precious moments in life getting upset over your mother...she does not seem happy..you are enjoying what you are doing...you go girl! I would much rather enjoy a "not so perfect" quilt that have it sit there as an unfinished top...
maybe you should have her read some of these posts and she may realize how thoughtless unecessary comments can hurt one's feelings...