I also would use larger squares and no batting. If it were mine I would put flannel on the back and I would increase my seam allowance to 1/2" as demim is thick and your seams will be difficult to lay. I have made a couple of denim quilts so I can speak from experience. I think your daughter will love it.

I started a blue jean throw size quilt for my niece to take to college, my brother insisted I make it to fit her bed, I did very earnestly try to explain this would be a heavy quilt. A few months later I did ask how the quilt worked out...nope too heavy.
Hindsight, I would have absolutely stayed my course and made the throw size.

Having finished a denim quilt recently, I would also recommend that you use larger squares for the quilt and use regular fabric with the denim square. I made one recently and found that it was very heavy and in spite of it being heavy it was not very warm. Go figure. A mixture of cotton fabric and denim would not only lighten the quilt, but would make it easier to sew. Oh, and be sure to buy a lot of denim and/or leather sewing machine needles. I went through 2 packs of them when doing the quilt. The weight of the denim when sewing the blocks together would somehow catch my needle because of the thickness of the seams and there would go another needle. Good luck.