For training, I'd put a caveson on her so she can't gape her mouth, not real tight, just tight enough to keep her mostly closed. Because of the difference in feel and materials, she's going to try to play with it for a while, but I'd only let her do that if she was bitted up and standing in her stall. No reins, no caveson, no saddle, just the headstall and bit, for like 30 mins 2X/day. She'll get used to it quickly that way.
When lunging, I'd tack her up and tie her head to one side or the other, NOT real tight just mostly tipped in, so that when she lunges she can drop her nose and give herself relief from the bit by getting her nose vertical instead of out in front. Lunge 5-10 mins left, then switch sides and do the same to the right. I wouldn't try to ride her until you see that she's dropping her nose and teaching herself that relief is when she's vertical and not fighting or trying to evade the bit. Once she's taught herself how to get relief on each side, then you can tie the reins on both sides so that she's straight and has pressure if she tries to raise her head. Then lunge her until she gets it with the reins on both sides. I usually take a couple of weeks to "put a face" on a horse, not a rushed thing.
Once you get on her, jog her in small circles and work your way out to a large circle without picking up speed. If she tries to speed up, go back to the small circle until she slows and then move slowly out to a larger circle again. You just have to do it til she gets it.
I forgot to mention, I'd start all that in a snaffle, not a twisted wire btw that's a horrible, harsh bit, and once she gets it in a snaffle, progress to a correction bit. I prefer this correction bit, it's very kind: Robart