Do you have someone to help you? How does she go in the hack you have now?
While I agree more training is the answer, if she is dangerous and completely ignoring you, and you don't have the physical strength to get her stopped...By all means, up her bit and ride lighter.
Sometimes, you can have a snaffle on and be yanking and pulling and get nowhere when you could just put a shank bit or a combo on and just respond lightly and then increase your energy until the horse gets the idea. It doesn't matter, but you must start light.
I am 110 lbs and I work with difficult horses. I am not physically capable of getting a bolting horse pulled around sometimes, by one rein or both reins. So, in that case, I tend to up to these bits: Billy Allen Bits | BuyTack - Abetta Horse Bits
A very nice transition bit. For you, I would choose one with a short, very curved shank and remember ride light!
Only pick up harder if he doesn't listen. Stop and back a LOT.
Have you tried maybe a snaffle with a nose band as well? You can tie a piece of string on the nose or order a real noseband. Anything you can find will work, like a piece of nylon even.