It is very difficult to tell a BFF that you can't do this for her. You might consider telling her that you thought a lot about the quilt and realized that you do not have the ability or skill to repair her quilt and that any further repair will probably not hold up either as the fabric is shredding. Suggest that she get a quilt rack to display it in the bedroom, or suggest she contact professional people who do quilt restoring.
I know I was heart broken when my mother threw out my favorite quilt that was in rags and I was an adult at the time! I would have loved to have that old quilt still around to look at even if it was not useable any more.