Color catchers are the key to the universe. They are in the laundry aisle. You may have to look a bit because they come in a box that looks pretty much like dryer sheets. They can be easy to overlook.
Don't panic. Everything will work out just fine. Remember, this is for your mother. Mothers are the ladies that love lumpy clay ash trays even when they don't smoke and keep paper chains you made for Christmas in kindergarden. Whe will love your quilt.