It sounds as if this poor cat has been under-stimulated for 9.5 long years! You might struggle to get her to play or interact now, but it’s worth a try.
You can’t change her lifestyle, sadly, but - as others have said - you can make some small changes for the duration of the sit. When we had cats, they too used to love the Cat Dancer and another favourite was those small white or grey mouse toys, though you could try things like tying a knot in an old sock (if you have one to spare) or getting some cardboard boxes from the supermarket for her to investigate. Cut doors in them and see if she’s interested in exploring. A scratching post or pad if you can afford it would be a lovely gift for her snd something she might enjoy after you’ve gone (and her pet parent might see her enjoying toys and take the hint). They also usually like thick hairbands, which you can stretch and twang.
You say she’s reactive to hands. I’d just stroke her once, then stop, but keep talking to her gently and tell her whst a good girl she is. You can possibly then increase to 2 strokes over the coming days, but always stop before she tries to swipe you (and always stop and turn your back if she does swipe you).
I feel sorry for her. Cats need mental and physical stimulation but it sounds like her life contains neither.