Do you have any other foals for her to follow, and if not his is what I would do. I would try to build up her trust, sit with her in her paddock or stall, rub and scratch her, brush her. then I would put her in the stall if you have a helper it would be nice, but sometimes you don't, get a halter on her, let her wear it for 15 or 20 minutes twice a day with supervision, then after a couple of days attach a lead line, let her wear that, supervised for a couple of days. Do not try to pull her it may injure her neck, try putting a long line around her rear end and through the halter putting pressure in the rear, that teaches her to use it. If you have a helper that is a good thing, they can push on the rear while you try to lead, sometimes they will act like a fish caught on the end of a fish line and hurt themsleves flipping over or whatever, you want to keep everything calm if possable. You don't want them to hurt themselves or be afraid of the halter or leading so trust is important. Go slow, mini's learn very fast. After they learn to give to the pressure of the halter you are ready to tie, if you have a buddy that already ties that is a plus. but if not stay with the foal anyway, tie them for a few minutes, do something pleasant, like brushing, scratching, then turn them lose, gradually increase the time tied, with the pleasant stuff but also alone, by the time they are acclimated to being tied up for one hour they usually are halter trained. Good luck, I'm sure other will help with advice.