Thank you for that, it did really help on the occasions when she got silly.
To a certain degree they allow her to get away with things like biting and scratching - things that my cats were brought up to know never to do - because it's just "what she does". The last time I looked after her she was a complete nightmare and it was a horrific week: she wrapped all four legs around my thigh and tried to bite it, she leapfrogged off my head while I was on the floor, she even tried flinging herself off the chair and biting me - unfortunately she ricocheted off my arm and when I stood up this look of "oh yeah, she's bigger than me!" crossed her face and she ran off... I was dreading looking after her again.
But this time she mostly managed to behave herself. (Of course, what worries me is when I told her owners that, they were surprised...!) Every time she got silly I decided I'd treat her like a child instead, so when she tried to bite or scratch me I told her off and then I ignored her. She's take herself off and sulk and then eventually come for a tentative cuddle. The oddest thing is that would never work with my cats who, like most cats, take being ignored as an indication they can carry on with whatever they're doing... The one time I did have to smack her (not hard, she's only small and I don't like smacking cats) was when she was jumping on the paper and wouldn't leave it; when I smacked her, she tried to smack me back! So we had more ignoring, and she sulked... and then she tried to sneak into my lap.
As I say, I was surprised in the end at how well we got along - much better than last time. It's just hard to remember to not be afraid to discipline a cat who acts like that...
She did bite her owners when they came back though. Apparently this meant that they were home...

*sighs*