How do you go about reminding them without seeming like a clutching tyrant?
The person in question has really just forgotten about it but I hardly ever see her to be able to bring it up in casual conversation. I lent her £25 just before Xmas as we attended a school event and she'd forgotten her purse.
A couple of days later she put a Xmas card through the letterbox but there was no money in it so I know she's forgotten about it.