Well she certainly has to learn how to accept people. Brushing is nice, but horses need to learn to enjoy it, they don't naturally like a foreign object being rubbed all over their body.
I would suggest separating her into her own rather small paddock, round pen if possible. Then get a good book and park yourself. Wait for her to get curious about you - this won't happen as easily if she has her pony buddies to hang out with. When she does approach you (I promise she will) do no reach out to touch her immediately, let her smell you all over like I'm sure she'll want to - let her run off and come back, you can talk quietly and calmly to her, but don't scold her for anything. She may paw at you if you're sitting though so be careful of this, do not scare her away if she does this simply pop your hand in front of her leg, it's going to be a curious pawing not an aggressive striking (if you haven't startled her), so just block it and say in a quiet low voice 'heeyyyy'.
Once she is willingly greeting you, you can attempt to slowly reach out and touch her, when you do make it feel GOOD - do not tickle her like a bug or pat her hard like a dog, scratch her and rub her make it feel nice. Finding her 'itchy' spot will make you her best friend. How horses bond with each other is by grooming each other, you can do the same, but don't introduce the brushes until she excepts you hand.
Once she accepts being touched - all over - practice 'giving to pressure'.
I'd suggest leaving the halter with a short rope attached to it all the time (about a foot, maybe less if she's that tiny, short enough she can't trip on it). Now when she comes to you and you can pet her, take the rope and rather than trying to pull her forward right away try teaching her to turn her head. Here's how:
Pull the lead rope either to the left or right, pull it just enough so it is taught, putting just a tiny amount of pressure on her face, wait, if she flips out you applied too much pressure, if she does nothing - very slowly add more pressure. This is the important part - the moment she moves, even an inch in the direction you're pulling, release the pressure and pet her. Practice this skill turning her head in each direction, toward and away from you until she touches her nose to her girth area with just a small amount of pressure. Remember the release of pressure needs to be timed just perfectly and needs to be consistent.
Once she is turning, practice the same thing, but taking a step forward - if she won't step forward try turning her but standing further away so she needs to take a step of two to be able to turn with the pressure. Practice this until she is leading consistently.
Once she is leading and turning her head then you can teach her to yield the rest of her body, her hind end and front end and backing up. You do each by applying a small amount of pressure to each area of her body, the moment she moves away - release and rub the area so she knows she did the right thing.
Once she is yielding and turning and yielding introduce as many new toys and tools as you can!
Good luck with your pony projects!!