Do you ride western or english??
After making sure the bit isn't too big or pinching her...
I'd put a drop nose band on her so that she can't open her jaw far enough to get her tongue over the bit. I would also put the bit up a hole for a while so it sits slightly higher in her mouth so make it harder for her to put her tongue over it. You will need to be aware that she will be more sensitive in the mouth if you do this so definitely do not hang onto her mouth of gob her.
It may just be a matter of discouraging the behaviour by making it harder for her. You say she stops doing it once she's working after a while, so by making it more difficult for her to do it initially she may just grow out of it once the work improves. If that makes any sense at all!!
As for pulling faces when you get on. Make sure you get on with a mounting block so you don't pull the saddle over. This can make them pretty stroppy! Also make sure your saddle fits perfectly, so she's not associating you getting on with pain.
If you check that everything fits fine and your'e not dragging her saddle over when you mount or thumping onto her back, I wouldn't worry too much. Pulling faces doesn't bother me, only when they go to make direct contact or try to move me out of their space will I react.
My coach's horse stands there while you're doing the girth up and pulls the most horrible faces, and will continuously bite his leg. Will never bite you though, only his leg. No point punishing that behaviour, he's not dominating me in anyway so it doesn't worry me ;)