I'm sorry that your question wasn't answered in a timely manner. We don't have many avian vets on this site. Yes, I would be concerned about such an abrupt change of behavior but because it's not pathognomonic (specifically indicative) of any one particular disorder, I would continue to observe Mango for more definitive signs of illness such as inappetence, regurgitation/vomiting, sneezing, coughing, increased respiratory rate, nasal discharge, conjunctivitis, and/or diarrhea. It's important to recognize that our pet birds will mask illness until they're no longer able to do so. This is a protective mechanism because birds acting ill in the wild will be attacked by other birds. Her eating normally, however, and normal droppings would belie her being so ill.
Nutritional imbalances are a common cause of illness in our pet birds. What has Mango's diet consisted of, please? Seeds should compose less than 20% of her diet. A diet of mainly seed and nuts has excessive fat, carbohydrates, and phosphorus; marginal protein; adequate vitamin E, and are deficient in amino acids, calcium, available phosphorus, sodium, manganese, zinc, iron, vitamins A, D3 (necessary for efficient absorption of calcium), K, and B12, riboflavin, pantothenic acid, choline, and available niacin. Ideally, a balanced pelleted diet such as can be found here: www.harrisonsbirdfoods.com or here: www.lafeber.com/pet-birds should be fed as well as hard boiled egg yolk, pancakes and cornbread, the tops of fresh greens, dairy products such as yogurt and cheese, fresh fruits such as apples, pears, melon, kiwi, and berries, vegetables such as broccoli, carrots, beets, asparagus, cabbage, sweet potato, and squash, and even tiny pieces of meat.