Using the backing is a good way to finish a quilt. There is a special ruler-like gadget that enables you to make a mitred corner easily--i bought one but i haven't used it yet; but i intend to do several of my UFO's that way.
do what your heart tells you to do and don't let anyone tell you differently. Our mothers love us dearly and often times they thing they are helping us, but they would help so so much more to just one time say something like, "that looks really nice". but don't hold your breath for that--just take deep breaths and know that your work is beautiful and will be appreciated by those who receive it.
hugs, carol/kittyquilt