Join-up is a way to bond with the horse. Monty Roberts teaches it in his book. If you have a round pen, turn the horse loose in it. You stand in the middle and get the horse to run around you. Keep your body facing the horse, as, this is confrontational to them. In the wild, to punish a horse, the alpha mare keeps them out of the herd. She faces them, and won't let them come in until she is ready. So, you keep the horse going around the pen, it doesn't have to be at a gallop the whole time, she can trot or even walk. Her inside ear will be on you if she is listening to you. Right now, you are the alpha mare, and you are keeping her out of your herd. Horses natural tendency is to be with others, so she will naturally want to be with you.
Don't let her turn and face you or stop until you are ready. You can make her change directions a few times if you want. If she starts to submit to you, she will lick her lips, open and close her mouth. That is a very good sign. When you feel like you want her back in the herd, turn sideways, so you are not facing her(confronting her). She will slow down and stop. (I personally did this with a very nervous gelding, and people couldn't catch him in the field, but I was able to walk up and pet him after this in the round pen and calmly get a halter on him.)
Of course, just brushing her, talking to her, and loving on her will give you a good bond with her too. For her tieing problem, I would start from the beginning. Tie her in a 'safe zone'. A place where you know she is comfortable. Groom her, pet her, love her. Make it a pleasent expierence. This method however, takes more time and patience than the previous methods, but personally, I think it is worth it. Anyway, the next day, move her a little farther (as little as a mere few feet, or where you think she can handle without freaking out) from where she was tied previosuly. Don't even tie her, just wrap the rope around another sturdy pole. Groom her, make it a pleasent expeirence again. Spend as many days as you think necessary until she it totally relaxed there. Then, move her even a little farther away. And, each day, you will be growing a stonger bond with her, so she will worry less and less about the other horses.
Eventually, it may take up to even a month, with the same process of gradually tieing her farther and farther from her safe zone, you will be able to tie her anywhere without causing pain and fear, she will have way more trust in you.