Yes, I too have a conniving mini. It would seem like the smallest ones would have smaller brains!? Noooo! I have played this game with my mini plenty of times. She needs to either be stalled daily and fed hay in the stall - so although she may not like it, that's where the food comes from, or you need to act like catching her is not a priority. That's the trick to catching skiddish or naughty horses. Patience and an indifferent demeanor. So - show you have the food, because that is a mini's strong weakness, but turn away like you are skiddish or weary as well. This makes a mini's curiosity go haywire! Curiousity gets the better of them, and their need for treats. So, squat down at mini- level, don't make eye contact, and just act relaxed and maybe even a bit subordinative - just a little. When she goes for the treat in your hand, slowly turn away, as if you arent super interested. Make her come around to you, and give the treat. Then show you have another, walk a few steps away, repeat. Do this a few times, and she will probably now be following you. Play around with this but at no cost do you let on that you want to CATCH her. They know better. This works wonders for abused horses as well!
Let me know how it goes! This works! Just spend some time, don't say a word, don't make eye contact, and only go for the halter really slowly when her guard is down. If she runs off, repeat the process!
Your only alternative is tricking her into a stall with goodies in it and creeping up on her once she is in and shutting the door. But you really haven't changed her mind at all that way - if anything she probably won't do it again.