Seek treatment in a hospital. Self-medication is never the right strategy for dealing with an eating disorder; whatever treatment is undertaken, it should be under the supervision of a doctor. Since most diet pills are unsafe for anorexic people (and generally not particularly helpful for healthy people either). Clearly, denying the problem isn’t going to solve anything.
Option B should be easy to eliminate. And while exercise is often a key part of recovery plans from an eating disorder, exercising ‘as much as possible’ is not the right approach. Instead, a person recovering from anorexia should stay active and engage in moderate amounts of exercise corresponding to their level of overall fitness. Exercise, denial, and diet pills are all potentially dangerous for an anorexic patient.