DS = Old style one, bit chunkier, slightly dimmer screen. Available in Blue, Silver and Pink afaik. Can probably only get them second hand nowadays.

DS Lite = New style one (been out a while though). Its quite a bit smaller, has a more vibrant screen. Available in black, white, silver, bright red, bright green, bright blue

As for Wii games, no idea on whether they can be chipped. You can download old retro games onto the built in memory, or extra memory sticks (From the snes, n64, nes etc.) which may mean you can run external ones from your own sources on there, not sure.

Wii games are only ever £40 max, but obviously 2nd hand is also something to consider for those, I generally found people take care of Wii games better than 360/ps3 discs, whether thats just the owners, im not sure.

But come to think of it, im not sure if it'd ever run *stored* games, because it doesnt have an actual built-in hard disk (Apart from 512mb or so of storage inside already), only uses memory sticks, which wouldnt really be enough to store wii games on. Can probably play copies though with some chipping I guess.

Hmm well the wii is definetely a console for family use (2-4+ player games for example) but it can be single player. I mean you usually use two controllers, one in each hand:

TBH she should enjoy either a DS or a Wii. Not sure how old she is? But girls tend to find alot of games they'll enjoy on the DS. Obviously on the Wii too, but depending on things she likes there's like:

Nintendogs games, Hannah Montana, Dora the Explorer, Pippa Funnell Horse riding games, Catz, Dogz, Rabbitz, Hamsterz, Dophin games, Mario Games, Sonic Games, theres Brain training games aimed at kids (brain academy) and adults (brain training), theres various other educational ones too if that was another benefit. You can also play old Nintendo Gameboy Advance games on the DS too, so that opens up to more games available, which you can probably get quite cheap from Gamestation etc. (Obviously going on the stereotype of what young girls usually buy for the DS)

And likewise you can play Gamecube games on the Wii.

edit: oh and lots of disney games on the DS too if she likes those. From some of older disney films, to newest ones.

Yeah she will know how to work it once its turned on, the game is in, the right icon has been clicked on etc.

DS lite all she would have to do is turn the power button on.