Sounds as if your mentor is taking all the fun & joy out of quilting. She's expecting you to sew like she does even though she has 20 years up on you. If you are going to pull the borders off because of a small mistake you'll take a long time to finish one quilt.
"If a blind man on a galloping horse can't see it neither can anyone else.
I hope this little poem may help you:-
Your own ideas are as good as anyone else's
Make yourself happy by making the quilt you want.
I've adapted that from a garden sign (seen when BFF & I went to the Carnival of Flowers in Toowoomba).
I had permission from the home owner to adapt & use it.