This treatment might work, if the clownfish is eating - and it's relatively reef-safe, though try not to drop the food straight into an anemone or coral:
Kanaplex, Metroplex and "Focus" are all products made by Seachem. Kanaplex is an antibiotic, Metroplex works as both an antibiotic and antiparasitic. Focus is used to bind the other medications to fish food, so that the fish consume the medication. Use one "Seachem measure" (comes with the medications) of Metroplex, one of Kanaplex ... and if using both meds, I'd use two of Focus ... per tablespoon of food, mix it in, and give it time to allow it to adhere. If you're using it with dry food such as pellets, moisten the food so the meds will stick to it. (I will note here, I have done this several times with Metroplex, and with API's "General Cure", but not with Kanaplex.) Then ... feed your fish. If a tablespoon of food is more than your crew will eat at one sitting, pop the leftovers into the fridge for tomorrow. Treat for ten days or so, then re-evaluate. You can go longer, if you'd like.
If the fish is eating, it may help with her mouth issue. It's also an excellent weapon against internal parasites, though that's not the issue here.
~Bruce