Kitties, something worked to my advantage (like everything doesn't already?) and here's how it went.
We were sleeping in the deep dark nite nite time and as it happens, though I didn't know it as I was reposing more near her knees, Mom woke up. Her ever present "gotta turn over" ordeal (for me). (well, for her too what with me there and all).
Anyway, she did turn over and settled nicely onto her left side (her favorite). Then, as she composed herself to drift back off, turns out she felt me walking the few steps ever so slowly toward her midriff. I got there, put out a very soft and barely touching paw tip to see if those were the covers on the bed. She felt that almost tentative touch and then, after encountering sheet and blanket, I probed again and hit the jackpot. Mom midriff. Oh, it was under the covers yes but a few firmer let's-make-sure probes with my delightfully tufted feathery paw, and I moved right on in and settled deep into her midriff. I settled instantly. The entire thing took a minute tops. First time she was awake for it.
Kitties, I KNOW she smiled. I could feel that smile in the night. She told a friend today that she knew she'd be trapped again or have to disturb me one..when she wanted to turn again.
That time did happen...she moved ever so easily onto her right side and found she was...where else? the edge of the bed. I, however, was firmly and warmly attached to her back---myself never having moved. I would swear she smiled again!