Ramachandran would not have a treatment for it. He just studies the mechanism. Zoobie's remarks are, as usual, misleading on the topic of neuroscience.
Phantom pain/sensations are what Ramachandran studies; he didn't "invent" the concept. It's not even his primary area of research.
What Zoobie alluded to, but didn't quite state, is the well-established idea that phantom sensations are happening at the level of the brain. Afterall, the receptors of the affected area have been removed along with the limb/organ.
Regarding internal organs, you don't actually feel an aching pancreas, for example. You feel pain in the back or abdominal wall. USUALLY the pain is referred to predictable places, but not always, because everyone has variations in their anatomy. And, the fact is that medical mistakes happen because of this.
Pain lasting 15 years is, by definition, NOT "acute." My first suggestion is before writing it off as phantom pain, find a new doctor and make sure the initial diagnosis was correct, the right organ removed, and that no other organs have been compromised. Also, is she carefully following the dietary restrictions that would follow pancreas removal?