Catching a horse
You have to make it the mares idea to come to you. Since she is the dominant mare(or used to be in a herd setting but still is with you) she might work well with this. Don't "chase" them. That is the usual flight or fight episode, which usually ends in flight away from you. She wants to play the game with you. I wouldnt use grain, except to reinforce it after she has either stopped and faced you and waited for you to walk up to her and haltered her or else walked up to you like a "lady" lol. If she walks away from her, shoo her away with your arms and make her work. If she is near you, she doenst have to work. She just has to stand there with the halter on next to you. If she is away from you, she gets to work. Don't make a big deal about it but get her moving with your body. Its all in the "language", just like mentioned above. Once she stops and faces you or stops and walks up to you and allows you to put the halter on, pet her and give her some kind words and then let her go. Don't shoo her away, just let her walk away from you on her own accord. Do this several times a day, like two or three even in short periods so she doesnt get bored. Make sure you always end it on a good note, though! Good luck! My one mare used to be really hard to catch but with this it really does work. Sometimes having more poeple to help you keep her moving so she can't slow down is effective too.
Shaneequah, 1998 gaited Bashkir CurlyxArab mare
Johnny Cash, 2001 Arab x pony gelding
Brighty, 2013 Standard Donkey jack