I wanna say it’s b but if not I’m so sorry !
Parasympathetic will return her heartbeat back to normal. This nervous system is responsible for regulating the body's unconscious actions, and stabilizes it.
This could be due to a malfunction of her thymus.
The thymus is a soft triangular shaped organ that is situated in the mediastinum of the thoracic cavity. The thymus is the predominant donor of cells for the lymphatic system. The thymus performs an important role in the training and growth of T cells (thymus-derived cells) that are produced in the red bone marrow. The T cells defend the body by destroying infected or cancerous cells and harmful pathogens such as bacteria, viruses, and fungi. The thymus also helps in the proper growth of other organs within the immune system.
The most likely cause of the burning sensation is acid reflux which travels back up the esophagus and irritates the esophageal lining. The chest pain felt can feel almost like a heart attack but it is best described as referred pain from the esophagus.
Should this heartburn persist, it is highly recommended to see a physician because the acid can erode the esophagus lining & the abdominal lining leading to ulcers. Easily treatable condition.
From a personal level this is awful!