You sound like you are employing the techniques correctly to me and I was going to vote for chasing since it was first suggested. Maybe it is just taking longer because those of us experienced with this lesson can get through it faster. Horses don't wear watches and I never impose time frames on their mental ability. If it takes longer it takes longer, she isn't going to hurt her horse by making it break a sweat a few extra times. I taught someone this method this summer then I handed her the halter and lead and said this is your battle. I walked away and in twenty minutes she had him caught, I could have done it quicker, but the point was made. She even said he got her to the point of wanting to give up and that was what made her mad and finally determined not to let him have his way, ie. make her retreat the arena. The next time it went faster, but still was a pain, probably wouldn't be easy for a long time but she learned how to catch any horse that day. Also just because we are teaching them that it is easier to get caught then avoid it, doesn't mean they are ever going to be that happy nice to see you horse that greets you every time you come. We can't change personality, only create ways to communicate the rules that are expected to be followed, they don't have to be happy about it, they just have to do it sometimes.
Troubled TB ~"A thorn by any other name will prick just as deep." @-'--,---