Now I've heard kittens should stay with there mama til there at least 12 weeks. So is that including nursing also? Even if they are eating and drinking on their own.
They will stop nursing when they and the mom are good and ready (though they may not be in agreement about the timing!). Mom's milk benefits the kittens for as long as they get it.
For all baby mammals, weaning is a gradual process. It starts as soon as they start eating solid food but it is not meant to be complete for some time after that.
Kittens need their mom for a number of reasons, not just nursing. She teaches them hunting, social behaviour, litter burying and hygiene. If possible, kits should stay with mom for 11 -12 weeks, while being socialised by human handling at the same time. If taken away too young, they can sometimes exhibit some behavioural problems later.