I feel your pain. My son is the same age, the only thing that got him to stop was a visit to the orthodontist. It wasn't to scare him, he legitimately needs help because his 2 bottom teeth that had come out couldn't come in properly because his thumb was in the way. For 2 years our dentist told us that no matter what we did, if he didn't want to stop he wouldn't. At his last visit in October, he said that he was going to need orthodontic intervention because of the deformity caused by his thumb sucking (nothing major, but bothersome). His orthodontist was super. He gave him the facts, including showing him pics of what his mouth could look like when he stopped. He also recommended a tongue crib, a contraption in his mouth to stop his tongue from thrusting forward. The deal sealer was when he mentioned that he needed to stop soon, or he may have to do surgery to correct some of the problem (the honest truth, not something he made up to scare him). That night, my son stopped, he now has his tongue crib in for the next year, and he's progressing nicely. The point to my long story is, maybe she needs an orthodontist to look at her since her adult teeth are coming in. That may be enough to get it through her head that she needs to stop. Hope this helps, and I hope that you don't need anything done.