Thanks for the suggestion, but she's happy with a magic mouse and a MacBook Air plugged into a display. I think the weight of the mouse really helps - as I said

Thanks for the suggestion, but she's happy with a magic mouse and a MacBook Air plugged into a display. I think the weight of the mouse really helps - as I said she's not shaking so much that Shake To Undo is triggered, so the intertia that the mouse provides is enough. It does make me wonder whether a weighted touch "pen" might be useful though. One of the issues is that she has quite big fingers, so it's easy for her to obscure what she's trying to tap on, particularly the keyboard in portrait, and if it's weighted enough that might help to counter the shaking.