Was a minister's wife for 43 years until DH passed away. I know from experience that the church is full of sinners that need forgiveness. Some for big sins and some for their know-it-all attitude. It is the wise woman who tries to enlighten them, but when they resist just walks away letting them continue to be wrong. The people who matter (those who love to quilt) know what it is called. You did a great job of handling her and the situation. Plus the example you set for the other ladies in the group (who are more than likely tired of her attitude also.) Another star on your crown in Heaven!
BTW my dear grandmother, who taught me to quilt, always called it sashing. She learned from her mother. Grandma was born in 1882 so the use of sashing for quilting has been around for more years than this wannabe. So there!!!