Thumbsucking is a self-soothing behaviour that arises from the need to soothe oneself. Remove the need and the behaviour will disappear. Trying to force her to stop doing something that makes her feel better when she feels bad is the best possible way to reinforce the behaviour for two reasons:
1. enjoyable behaviour that is pressured becomes persistent (the 'you aren't the boss of me' response) and,
2. if she's doing it to alleviate anxiety, making her more anxious will increase the incidence, not diminish it
You could teach her to replace this nervous habit with another one, but that's hardly a sensible approach. That's like teaching a baby who needs mom's warm loving arms that a blankie is 'the same enough' and then trying to take the blankie away because of impatient with the child's neediness.
I'm not sure why you think her permanent teeth have anything to do with this --the suction (particularly vigorous suction done frequently or for hours on end, like through the whole night) cause dental damage by distorting the upper jaw's development... whether the teeth are in the jaw or out of it.