Also, on the nipping, 2 other things you can do. When she acts "nippy" keep an eye on her. When she gets 2 mouthy, preferably before she does nip, take a hold of her chin whiskers and pull. It's irritating and she'll "forget" what she was going to do.
The other thing, if you are down where she is, keep a limb in her way... basically, you still have to pay attention to where she is at all times. Then you block her teeth as she reaches. Don't go out of your way to "hit" her but a bump will make her think she's run into something and again, she should "forget"... If she's persistent, than really use your voice and even a knee to bump her mouth. Works well. Can be hard to develop that "6th sense" of where the foal is - but it's in yours and your families' best interest...
The main thing is paying attention - even when you just want to love on her. Consistency is the thing. Some mares let their foals just "get away w/ everything" (biting, chewing, pawing, kicking, climbing on them) and that carries over to the 2 leggers in the foals' life. It is hard for a foal to understand that that is not allowed! But it's not and never should be.
I personally also don't allow hand feeding of our ponies/minis. They seem to have a lot more of an issue (than larger horses) with telling what is the treat and what is the hand - especially when a little hand smells/tastes the same as the treat (until a finger is removed! and yes, I've seen this happen 2 times with minis!!). We put treats directly on a pile of hay or in a bucket most of the time. Now that I don't have small children around most of the time - I AM working with some mature ponies with treats - but it's very limited and it's only w/ a couple of special cases of MATURE ponies - not the young ones...