The most appropriate treatment is fluconazole. This patient has a clinical presentation and findings characteristic of Candida albicans esophagitis. Infectious esophagitis can be caused by bacterial (uncommon), fungal, viral, and parasitic pathogens. Patients may be asymptomatic, but common symptoms are odynophagia or dysphagia. C. albicans is the most common cause of infectious esophagitis in immunocompromised patients and is often associated with oropharyngeal candidiasis. It often presents with dysphagia, odynophagia, and curdy white esophageal plaques seen on upper endoscopy, which is confirmed with esophageal brushings. This patient's immunocompromised status after liver transplantation puts her at risk for Candida esophagitis; however, Candida infection can occur in immunocompetent patients as well. Candida esophagitis should be treated with fluconazole.

The differential diagnosis also includes possible viral causes. Cytomegalovirus often presents with a single ulcer in the esophagus. The diagnosis is established with biopsies from the ulcer base, and treatment should be with ganciclovir. Herpes simplex virus is also characterized by ulcers, typically multiple, found on upper endoscopy. The diagnosis is established with biopsy of the ulcer edge, and treatment should be with acyclovir.

Swallowed aerosolized glucocorticoids such as fluticasone are often used as a treatment for eosinophilic esophagitis. Patients who respond typically do so quickly, but symptoms often relapse when the treatment is discontinued. Esophageal candidiasis is a side effect of this therapy. Treatment with swallowed aerosolized fluticasone is likely to exacerbate, not improve, this patient's symptoms.

Fluconazole is the first-line therapy for Candida esophagitis and is a more effective therapy than swallowed nystatin.