There are several reasons that an heirloom will deteriorate-long time use as a bed cover, quality of fabric, environmental conditions, etc. People need to understand that if they use a quilt and not keep it in museum-like standard air conditions it will suffer damage. I would suggest you ask your friend to go to a quilt restoring service and talk it or go with her to a quilt appraiser. That way you free yourself from emotional involvement and trying to do a task you may not be equipped to do. Restoration involves far more that just repair of rips, etc. Suggesting display in some fashion is probably the best idea. Since your friend does not appear to know how to properly treat the quilt in question I'm sure she does not understand the reasons for deterioration and that she is contributing to it. Have an honest conversation-your lovely friendship will not suffer for it.