That's a great top!
I would also leave it, no extra fabric to worry about. It would be nearly impossible to find, I think.
So nice that you have something that old from your family.
Welcome to the board :)

To do or not to do? What a thought when coming to finishing a vintage quilt. I sounds like you GM's aunt was a do as you go kind of person so I would finish is in a likewise finish. Put a wider binding on it and call it a day. Enjoy the beauty of the quilt as she intended. It is in our nature to make things perfect but this quilt is not intended to be perfect. You said it right, a utility quilt, to be used everyday, throw on the floor or take to the beach and shake the sand out of kind of quilt. To keep you warm at night and carry to the sofa kind of quilt and sit in front of the fire with quilt. Finish as she would have and then you have a true memory of your family and what you inherited.

I suggest you just put a border on it or just bind it as is. This is such a treasure and you will lose the points on the blocks but it would be way too much work to replace all the muslin triangles. Just enjoy it as it is and have lots of memories with it.

She did a great job of laying out that top. Is it hand pieced?

I am almost wondering if "someone else" cut off the setting blocks like that?

Whatever - I agree with the others - leave it "as is"

If it were mine - I would stabilize the edges with staystitching - and if I could get it to lay flat, I would bind it and call it "good enough". I think the majority of people looking at it would not notice - or care - about lopped off points.

Just finish and love it. It looks so comfortable and a treasure.

I’d cut new setting triangles to preserve the points. Muslin or white cotton. Whatever is closest.

Finished!
 

60 years later, the quilt is finally finished!

It looks great!! I"m sure you are happy it is done! I love it.

That looks fantastic!!
I always smile when I see old quilts that have pieced pieces!! I have some of those :)

Beautiful!