No children at all. I don't have any photos of her either as we only met recenty. She was my maternity cover and has done a great job and wanted to say thank you to her for that. I think if she had stayed we would have been good friends and plan to stay in touch.
I second a good travel guide book, to Hong Kong or the region.
Or something personal about the life she's leaving behind in the UK - a framed print or arty photo of the city or town she's from, for example. When you move to a new place, in a new country, one of the things that makes your new house a home most quickly is pictures on the wall.
Maybe it's just me, but I've always hankered after a nice set of luggage tags / travel document-holder. They're not the kind of thing I'd buy myself, but living in another country and travelling back and forth a good few times a year for visits etc it's something I'd quite like to have.