I think you should leave her stitiches in. While it may not look perfect, in years to come, they will be HER stitiches and you will have fond memories of the hard work she did. It may not wear as well, but if all you wanted was a blanket, you can find that at Land's End. I think so much of quilting is the work of the person who made it, and you should consider that in your decision. But at the end of the day, if it will always bother you to have stitching that shows - then the work to redo it is worth the time.