So if I understand correctly, you can't get the bit in her mouth?
If so, you need to start by teaching her to lower her head. Most people will say gently press behind their poll until they ever so slightly give to pressure, then release your fingers quickly to reward them for giving their head. Repeat a gazillion times before attempting it with the bit.
I helped things along with my gelding by holding treat down low in the same hand that I am holding the bit, and kind of ask him to take the bit with the cookie. The first several times he still threw his head up but eventually I got to where I would present the bit, held nice and low, and he would take it and THEN I would give him a cookie. My gelding is very food oriented that way.
You know what? After re-reading the post, it sounds like you really have a tying problem, even more than a bitting problem. Not taking a bit is certainly a problem, but ripping trees out of the ground is even worse. Maybe someone with more experience can offer some typing advice. Your horse should give to halter pressure and not fight until she frees herself.