Here's what you can do, find the mildest bit possible (full cheek french links are my favorite) and put it on her. Take the reins off and watch her carefully, let her be with it for about 10-15 minutes (maybe groom her the whole time to keep her still). Do that a couple times, putting something yummy on the bit (they make bit wipes - I just use a fruit roll up) will help make the bit a little nicer :)
Once you can put the bridle on and she just stands quietly with the bit in her mouth (without fussing it around), then you can practice her giving to the bit. So pop the reins back on and stand next to her on the ground. Hold one rein, with your hand rested on her withers so you don't pull more than you should. Hold it so the rein is taught and wait. If she does nothing at all slowly increase the pressure until she starts fussing - then hold that pressure. When she starts fussing hold the same pressure until she turns her head towards your hand - immediately drop the pressure completely and give her a pat. Repeat this in both directions, standing on both sides of her (so sometimes she turns to you and sometimes away). Always start with the least amount of pressure possible and gradually increase if there's no response, if there is a response but not right just hold it and wait.
Practice this until she turns her nose all around to her sides in both directions, then practice the same way but holding both reins to get her to back up.
Once she's great with that practice on her back :)