I know you would want to respect your mother.But I do not believe in luck good or bad.We can not live in a superstitious state. In the mountains where I live there are so many older peolpe who have many superstitions ,I would not be able to get anything done if they knew what and when I planned to perform a task. So I would finish the quilt, but out of your respect for your mom just don't tell her till your are done.Tell her your love for your grandmother was what compelled your actions.