Do you have a budget ?
Most camera shops do second hand and usually with a warranty. So you'd have some come back if anything was to go wrong.
The D40 and D60 are quite old now, the D60 was replaced by the D3000 and seeing as that's just been replaced by the D3100 you might be able to haggle with the shop and get one cheaper, as I said though I don't know what budget you're working to so difficult to advise, I'd image you could get one of those for about £250 or thereabouts.
The D3000 is a great camera as it contains a really useful 'Guide' mode, it explains what settings achieve what results as you use them and when to use them, it would help her understand what she needs to do more with each control. That said the D40 and D60 are both great camera's and I'm sure you could get one real cheap if you hunted around. London Camera Exchange and Jessops both do second hand camera's, they're nation wide so you could try them ?
Your very brave letting her share your lenses