i make lots of flannel quilts- i generally use hobbs 80/20 batting. it is lightweight, adds just the right amount of cozy loft- an additional layer of flannel makes a very flat heavy quilt- a layer of batting gives it a little loft- softness & body...just my preference.

If it's warmth she wants, try a wool batting from Quilter's Dream or Hobbs because they are also very light weight and easy to quilt.

I, too, have RA and find my wool batted cotton quilt is my go-to quilt for 8-9 months of the year these days. Because of the RA, I find I'm more and more inclined to use wool as my batting.

Jan in VA

I made myself a flannel quilt and it is the 'go to' quilt for sitting around watching TV. Nice and warm! I had a bunch of flannel fat quarters I cut and pieced for the front and used a single piece of flannel on the back. LOve, Love, Love it!!

I just finished a string quilt made of flannel strips and I am going to back it with minky, with no batting inside. I am quilting this one on the LA, first one to do like this.