I would try this:
It's got a low port, it's slightly mullened out for tongue relief. It's also designed in a way to reduce/block the extreme nutcracker action of a single jointed bit. You can also purchase it loose ring I believe, but I like full cheek or D ring, assuming she doesn't lean on the bit. The loose ring may pinch her lips, but the solid bar on the ring provides a push to back up your pull. It pushes her nose over from the other side.
When you get a new bit make sure to give the horse plenty of time to just wear it and figure out how to hold their head to avoid pressure. This bit is ideal as it keeps all contact off until reins are used. And obviously, I'm sure you know, start with the lightest contact you can and immediately release at any solid attempts to do the right thing.
That's my suggestion, I haven't met many horses not comfortable in that.