x-post with Easterchocolate maybe, but here goes...
I'm a contact lens optician and so I've read this thread with interest.
I was fitted for lenses when I was about 15 and I had some yearly soft lenses as there was nothing else on the market. They were awful and I overwore them and gave myself 'veins in my eyes'. There was a scheme were you bought the solutions from them, and they would mark if off on your file and when you had bought 'enough' then you got a new pair of lenses. My lenses would sometimes be really old by the time they got replaced and they were horrible. My Dad didn't want me to have the gas permeable ones as he thought they would make my eyes look big
. It's not true, but there was a girl lived down our road who wore them and she had big eyes anyway so I think he thought I'd look like her or something 
I'm about -6 and I wouldn't give my lenses up for anyone. I wear the monthly high oxygen ones which I can sleep in if I want to. I had a check-up a few weeks ago and my eyes are fine.
The gas permeable ones are great as they let in TONS of oxygen to the eye (not the original hard type from long ago that didn't). They cover high precriptions and as long as they are looked after properly and you go for your check-ups when you're called then they can last a while.
Modern soft materials let a lot of oxygen in BUT there is an average wearing time of 10-12 hours for the 'average' adult-less for kids. The only way to wear them safely for longer is to go for the latest materials which are silicone hydrogel. They come in monthly / two-weekly disposables and in dailies, but there are only 2-3 brands on the market for these so if you want them make sure you ask for them and take your opticians advice if you are suitable or not.
They let the eyes breathe normally under them and will give a longer wearing time.
'Normal' dailies will NOT give this safely day in and day out. I am constantly surprised by the number of people I see who think that 'daily' means 'all day wear' and not 'daily disposable wear'. They are daily disposable instead of monthly or annual disposable. So unless you get the latest type you may be leaving yourself open to problems.
Having said that, I have some very young kids wearing lenses with no issues at all. My youngest is 7 and uses them for sports etc. Most of it comes dowm to you as her mum to make sure she washes her hands and cleans them etc. Make sure you ask questions at her check-ups and get all the information you need. The ACLM website is a good place to start aswell as the General Optical Council website. Can't make links work-sorry!!
Bootilicious is right about taking them out early and having a day off. Even if she has got the latest type, it's still good discipline to do. Her eyes are still growing after all.
Don't worry about the distance that glasses sit from the eyes, Revolting. Those groovy specs in the eye test room are at a certain distance and the glasses should match this so that extra effort doesn't need to be made IYSWIM. If the glasses are too low then take them back and get them altered.
You shouldn't ever really get someone suggesting a better lens for no reason. If they have suggested them, then take their advice.
Good luck! 