I think she is battling Hashimoto's disease. This is an autoimmune condition which slowly attacks and destroys the thyroid. Some of the symptoms are extreme tiredness, nervousness and body aches all of which Patsy has demonstrated. She is also on a dairy free, gluten free diet, which is recommended for people with an autoimmune issue and Perez did that bizarre nomination of her being the weakness with autoimmune problems.
I could be wrong though..