This entire thing gives me an incredibly bad feeling. First of all, your mom and cousin were running behind her. Since when is chasing a freaking out horse a good idea? I mean seriously people, common sense. Chasing a freaking out horse is just going to make it worse.
Second of all, you said once you stopped her you hit her a few times and then decided to put her in the goat pen as punishment because she 'didn't deserve to eat hay with her friends'. I guarentee you, that mare is NOT going to make the mental connection between misbehaving and being hit/putting her in the goat pen. Horses don't have that long associative memory. You got emotional, lost your temper, and dealt with it badly.
Thirdly, after your horse was misbehaving, you STILL decided it was a good idea to lead with just a halter. Are you looking for a Darwin award? I can understand being upset with the bucking and bad behaviour earlier, but this one was your fault.
Fourth, reading your second post, she's not your "little powniee". She's a horse. No matter how much you think she 'loves' you, she is STILL going to be a horse. Horses behave like, guess what? HORSES. Ergo, there is always that unknown factor of not being entirely predictable. Plus, she was in pain.
How to fix it:
1. Attitude adjustment. The only two emotions that belong on the back of the horse is patience, and a sense of humour. You owe it to your mare to be fair and reasonable at all times. You losing your temper isn't something she should have to deal with. Punishment should be delivered swiftly, with impartiality and a cool head. If you're really mad, take a bag of marshmellows, go behind the barn and throw the bag as hard as you can at a tree, until you feel better. Doing stalls and scrubbing blankets is a great way to blow off steam too. Pretty much anything where you can work your anger out without affecting the horses.
Along with the 'will not lose my temper', you need to understand the nature of horses. You can have a great relationship, but if she's in pain or scared, she may behave badly. The best horse in the world is still a horse.
2. Get a saddle that fits. Don't ride her until then, just work on ground work. Additionally, I'd get the vet, chiro and/or massage therapist out to give her a work over. Chances are she's in pain somewhere else, due to riding with a badly fitted saddle over a period of time. It's not fair to your mare to ride her if she's hurting.
3. While you're waiting to get a new saddle, do lots of ground work and stuff. Give her a bath, groom her until she sparkles. Pick up a book on equine massage therapy and learn to give her a massage (I'm telling you, horses LOVE it). Work on lunging, ground manners, walking/jogging/backing in hand. Do carrot stretches, work on vocal cues etc...
4. When you get a saddle that fits, I'd invest in some lessons with a knowledgeable trainer who can help you out. You sound like you're getting frusterated and in over your head. A trainer can help you learn to enjoy your mare, instead of being frusterated by her.