I think the holes throughout the background, sashing, and cornerstone fabrics indicate the fabric has "rotted" and is not sturdy enough to applique on or salvage in any meaningful way. I would find similar colored fabrics and cut out the butterflies (since they seem intact) make a similar looking quilt w/the new fabric and the butterflies.

Yes, I agree with kassandra...fabric has indeed rotted.....no sense in putting good money after bad. Just cut the good butterflies out and either reblock them or just make pillows or frame them.....

I agree with Tartan. It is exactly what I would do.

Yep, I would cut squares of the butterflies and then make a "background" using new pale blue and pink fabrics. I would applique the squares onto new fabric perhaps reinforcing them with backing just in case they are "holey" or weak fabric too.

I would check all the fabrics first and see if they are "sound" or "iffy" or "very weak"

I found some blocks my Mom had made - and they just tore more easily than bathroom tissue - and they were maybe from the 1950s or 1960s. I think they were a poly-cotton blend. They looked "fine" - until I tugged on them.

It looks like the most damage is in the sashing. The butterfly blocks look fairly salvageable. If it were mine, I would remove the blue sashing and save as much of it as I can and sash with some other fabrics and put the blue fabric as corner stones between each sashing. I am sure you will get a lot of advice on this board and good luck to you. Yes-it is salvageable for sentimental reasons for sure.

I assumed the holes were from mice.

What does it smell like?

If sort of funky, a good airing in sunshine might work wonders. I also think sunshine is a great disinfectant.

Then press it - that might give you a better overview of how much damage there is. After you see how much there is altogether - then show us some more pictures and you will probably get more suggestions.

It appears that the butterflies are all in relatively good condition. Could they be cut from the quilt top and re-appliqued on new fabric?

It is a beauty, and I can both see and understand the desire to save it.

I agree with Nanny's dollface, Prism99 and IceLeopard. Anything to preserve the original. It's a beautiful quilt top. Your mother will cherish it no matter what you decide. Good luck.