You need to spend some time learning horse 'psychology'. Watch horses in a herd setting. There is a definite pecking order and those that are at the top of the pecking DEMAND respect by biting, kicking, laying back their ears, and smacking around those that are lower than them. The lower ones soon learn their place in the order and meekly stay out of the other's way.
Your mare has determined that she is the boss of the herd and that you are down on the pecking order. You need to reverse that. You might want to take her to a knowledgeable horse owner/breeder who has lots of experience in "fixing" problem horses - where they will not be training your mare - they will be training YOU. Only when you know HOW and WHEN to apply certain techniques will you be truly successful. You CAN be firm and demand her respect without being abusive. You just have to learn how.
You have received LOTS of different suggestions here. Some might work, some won't because your mare has you completely under her control. Once you and YOUR trainer determine what will work, you need to be consistent in doing things....not 5 minutes of one technique and then 5 minutes of another. Flitting back and forth between techniques will only serve to confuse her and frustrate you.
Here's an example. A neighbor and good friend bought several miniature mares but really knew nothing about how to handle any kind of equine. The farrier went to her place after doing my horses - called me and said he was not going back there again unless I went along. Apparently one mare decided SHE was the boss - up in the air, striking, lunging forward, etc. which can be quite dangerous. Now, this was a mare who had previously been owned by someone who really knew what they were doing, but this mare was SMART and quickly learned she would be able to get away with this. So I went down there - took a soft rope and put a loop over her nose. And any time she so much as moved a muscle she got the tar jerked out of her. She snorted, she blew, she tried to strike, and I would jerk even harder. (I was sore for about a week.) But after about the 3rd go-round she stood like a rock and never caused a problem ever again. BUT - this is NOT something for the novice to try. I have been handling horses for over 45 years and I knew what/how to do and I knew this mare just needed an attitude adjustment. If she had been a scared, half-wild little thing - my approach would have been entirely different.