And my soapbox is:

Download a variety of Waltzes Here. There are 46 of them in varying degrees of difficulty and they're all written in ABC Notation.

If you download AbcMus (and as long as your niece has a PC and soundcard), she can play them anytime, at any speed, in an alternative key if necessary and with guitar chord accompaniment. Or just play several bars repeated over and over. There is a danger that you will be made redundant however!

I can send you the sheet music as an Acrobat PDF high quality file of this collection if any of these tunes strike your fancy. Doing the lot is as easy as just one or two. Send me a PM.

Best Wishes,
John