This.
radish said:
Support your local skate shop
Consider a Powell mini logo deck as they are a bit shorter in length than a standard deck.
Don't get pulled in by the shiny, expensive designs. Equally, don't buy the cheapest, unbranded, blank deck either.
I recommend a UK deck. Not only are they cheaper than the bigger name US companies (£30-40 vs £55-65) they're almost always the same. I ride a store deck from Note in Manchester (http://www.noteshop.co.uk/" onclick="window.open(this.href);return false

and it is one of the best I've ever had.
As for width: depends on shoe size and preference. But because she's new I'd probably get something mid-range; 7.75" most likely. Get her to stand on a few different widths (ideally with trucks and wheels attached) and see how it feels.
Trucks: width shouldn't be wider than the deck. Light is good for little'uns but to be honest there's not a lot in it. I advise most beginners to start on Ventures because they're cheap. I ride Silvers because they have inverted kingpins (the nut is in the base plate) because they give better clearance for grinding but I don't think that's a biggie for newbies and if/when it becomes a problem just take an angle grinder to the bolt and nut to clear the base plate anyways!
Wheels: most beginners won't notice any difference in soft vs medium vs hard. Soft are a bit quieter but obviously don't last as long and are more prone to squaring off (so become less smooth and quiet).
In terms of size: probably start on a 44mm. Again don't be pulled in by designs; they will rub off within a week or two. Solid colours are the way to roll.
Bearings: don't be brought in by ABEC ratings. The impact on bearings from riding alone wears these tolerances away in no time. You're better off buying cheap and often. A friend of mine bought a £60 set of Bones Swiss and they lasted no time at all. Sure, they were smooth as hell on day 1 but that feeling won't last. I tend to buy unbranded bearings for about £6 a set from a local bearing shop. Keeping dirt out, riding with spacers and washers whilst having everything tightened up correctly will make your bearings last longer than any ABEC rating rubbish. While I think of it; later on in skateboarding life go for ones with removable sides so you can clean'em and lube 'em up properly... I'm actually too lazy for this, but hey.
Grip tape: any decent skate shop won't stock the crap they put on Argos skateboards, so don't worry.
Risers: get them. 1/8" will do.
Bolts: ask the guys in the shop. I bought the wrong length last time and so am mis-remembering what I've got on :lol: Basically try and get a set that doesn't leave any excess bolt sticking past the nut because fingers inevitably get caught on them. Most sets come with an extra colour or two which can be used to indicate the nose ("front") of the board when fitted. Useful feature!
Last up, and quite importantly: don't buy anything made by Fracture.