I'm thinking of getting DD (7) one of the technic range, some of the vehicles have a pullback thing so they actually move which is cool. She did say she wants a lego house too so I'm thinking one of the creator range - there's a treehouse, a beach house and various others I think. Or the creator one that transforms into a dinosaur...
It's so hard to choose, there's loads out there! DS (5) will be getting lego too, and this Xmas for the first time SO AM I!!! Really excited, I've never had my own before so I specifically asked DH for some :o
Numpty it depends if she really wants to build a particular thing, and if she's ready for instructions yet. My two started at 5 and 3 with a huge box of basic bricks and a couple of baseplates, it was only more recently they've started getting the creator sets and building them by themselves.
If you aren't sure then I'd recommend a big box of bricks for open ended fun, plus one of the smallest creator 3in1 sets (the latter are around a fiver) to see how she gets on.
I wouldn't bother with the lego friends stuff if she's not asking for it, it's really dull - even DD totally ignores it in the shop.