Warm & Plush is 50% puffier than Warm & Natural. It isn't as easy to find in all the JAF stores, but I never struggle to find it online. I really love it! I ordered a 25yd x 90" roll from walmart.com and am thrilled every time. The only thing is that that extra thickness does add some extra weight. If she wants something that is light like a comforter, poly is probably your only option (or a poly-cotton blend).
Edit: Just saw your second question ... regardless of what type of batting you use, the heavier you quilt it, the flatter it becomes. You really don't want to leave more than 2-3" between your quilting lines if she is going to be washing it on a regular basis because wider spacing will result in more tension on the thread/fabric and the threads can weaken or snap over time. If you quilt closer together than that, though, it will be less puffy.
Last edited by Bree123; 11-03-2015 at 10:26 AM.