I'm assuming that the issue is putting the bit in and not the bridle itself? Otherwise, I would guess that you'd be having the same issues with a bitless bridle. Over the summer I worked with a TB that was super ear shy, but he would take the bit just fine. I wasn't tall enough to reach up and make it a quick task, and he would throw his head and shoot back if I touched near his ears. Taking the bridle apart on the left side, putting the bit in his mouth, and kind of tossing the right side over his head and then fastening it worked for me. We were taking it slow and making huge progress with it when I stopped working with him, but I sure wasn't gonna let him get by with not having that bridle put on and not being ridden :P
It sounds like it's a bit issue, but I'd make sure. The way you manage it changes... if it's a bit issue then trying to desensitize her to having her poll touched won't really touch on the underlying issue. Obviously, my first guess would be to get her teeth looked at. My second guess would be that the bit of your choice is not working in some way.