She cannot feel what should objectively cause her pain, but because pain is a subjective experience she can’t. However, truly subjective pain, that is pain derived from emotional connection, is literally the worst pain she can feel.
The guy couldn't emotionally recognise his mother after seeing her and started calling her imposter. But when he heard her voice over telephone, he felt emotional connection and said the person on other end was indeed his mother. Emotional pathways provide salience information in conjunction with sensory pathways. Any disruption to emotional pathways can override even correct sensory data.
Same idea with hunger and weight gain or loss. Hunger is a biological process. You can push through it, but people also experience it differently because their actual hunger mechanisms differ, not just because they "interpret" it differently.