comments:
Get a free standing ballet barre like this. They break down flat, and are designed to handle several hundred pounds. You can slip the PVC railing sleeve over the bar if you want, but you don't need to since sitting on a 1.5" pipe is plenty uncomfortable. The height adjustments are usually 4" increments, which probably isn't granular enough for what you want to do, but that's easily fixable by putting a couple of books on the floor to stand on. Alternatively, you can put books under the supports on one end to raise it up so she can adjust the pressure by shifting forward/back. 1.5" is a standard size for kee clamps (the structural pipe fittings you see in a lot of bondage vids), so you'll have more options for future stuff as well going with a barre using that size pipe.