I would likely work off lead, for a long time, as well as gaining respect on line...just simply getting her to move her feet in the directions I want; if she's nervous, just work with her calmly and continue until she starts showing some signs of relaxing (slowing down, licking lips, stopping, etc). The first few sessions in the round pen may be down right 'brutal', in that you may feel like it's never going to get anywhere, but just stick it out. Do lots of direction changes, and keep her moving in atleast a fast trot. Because she's an Arab, you will be out there for a long time, until she realizes that you are a worthy and acceptable leader.
I worked with a filly last year who, though wasn't 'as' aggressive as yours, took a long time to "get" the round penning thing, because she just wanted to be in charge...we were both pretty sweaty before she realized that she could relax and accept me choosing direction, and speed, and eventually backing, etc, off lead. I was really close to throwing in the towel, too, but I just kept at it, and the light all of a sudden went on; she stopped rushing around with her hip toward me constantly, started tipping her nose in instead, and was paying attention to my body, then she started chewing; when I asked her to stop, she stopped and turned in and look straight on at me, instead of giving me her butt. It took couple more sessions before she consistently obeyed off line well, but it was totally worth it; she was much more focused on me, and less focused on the other horses, and what SHE wanted.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."