I've noticed that being on antibiotics can sometimes cause frogs appetite loss. Do you know the temp and humidity? Was the spring water bottled? Some bottled water brands can have levels of chlorine safe for humans but not for frogs, I've read. Dechlorination solution is generally needed.

When frogs have tongue problems I tend to think Vitamin A deficiency but you'd been giving supplements, so it's probably not that.

Don't be too hard on yourself, you got her to a vet. It sounds like you really did your best. (Also I am not a vet, take my advice with a grain of salt.)