Encourage your sister to keep quilting. No matter how long she quilts, there will always be the "quilt police" that are so insecure in their work that they have to criticize others work. I have been laughed at for not knowing how to use a rotary cutter when I first started quilting about 2 years ago. I went to the LQS to ask someone to show me how to use the cutter. Then I signed up for a class and the same lady was helping with the class and she told everyone in the class that she had a lady come in that couldn't use a rotary cutter and she had to show "her" (me) over and over how to use the cutter. She and everyone in the class laughed hysterically at my "dumbness". Of course the lady didn't remember that I was who she was joking about and poking fun at. So now when the "police" say something stupid to me now, I just look at them and go away laughing. They are so pitiful in their arrogance.
The closest I ever get to perfection is when I am on my knees praying to Jesus as He is Perfection and no one else nor anything...