PAX hanging on...
I had one a few weeks ago. Not quite the same problem, but required a bit of ingenuity to resolve. This was a Starlight Day flight (chronically / terminally sick kids plus siblings / parents etc). One of my passengers was a little girl who had to be carefully handled in to the aircraft (she had some tubes in). She didn’t say anything, but smiled happily through the start up and taxi out.
At the top of the climb out I seemed to need a lot of trim to get the nose down. Looking across, my young passenger had got a good grip on the right hand side control column and showed no inclination to let go. The solution involved slackening her seat belt shoulder strap and putting a cushion behind her so that she could still reach the stick when it was further forward.
The rest of the flight went well and she seemed to enjoy it. I learned to brief inexperienced or nervous passengers to hang on to the seatbelts, rather than the flying controls!
Safe Flying,
Richard W.