I may be wrong but if you are going to re-write the pattern for your personal use I can’t see there being a problem.
If you ‘lend’ the pattern to a friend I can’t see a problem with that either.
But I’m sure it would be wrong to sell the pattern, even if you did give credit to the designer.
Is it not possible for you to ask the quilt shop owner? Perhaps you could say that you love her pattern but have re-written it in a way that you find easier to follow.