No child should have unguided and unchecked access to the internet and certainly shouldn't have access to your credit cards.
When children are smart it can be easy to think they can handle things.
But they are not wise. They are not worldly. They are not experienced. And they most definitely are not adults and should never be treated as such.
The internet can be as dangerous a place as the rest of the world. Protect your little one and her friends from herself. At the moment it's innocent online games, as far as you know, when does it move to innocent chat room? Remember you never know who is in those games with your children who is in contact with them. We should be more scared of letting our kids roam the internet world as we are with the natural world there are just as many threats there albeit of a different nature.
It is scary to me to think not only have you let your daughter roam the net world unattended but your little girl's friends' parents have done the same as well. Too many of us are too complacent when it comes to protecting our children.
I hope you have alerted your daughter's friends' parents to the little scheme they had going because they are obviously smart enough to work around their care givers once - they'll at least try it once again.
I would be more concerned about the excessive freedom your daughter has, her obvious disregard for the rules and her ringleading than about the screen time.
I hope you manage to get this under control before the hormones hit (and they hit earlier than you might think!)
PS there are exercises to improve eyesight and correct muscle weakness in the eye. You can google them easy enough. I'd be inclined to give them a go. My sister and I were prescribed glasses at the same time. She wore hers and just kept getting thicker prescriptions. I never wore mine and did exercises instead and my eyesight has not degraded and is in fact better. Though they don't always work as it depends on the problem it's worth investigating.