Insulin Resistance and Metabolic Syndrome: The patient's obesity, uric acid stones, and elevated urinary sodium suggest a metabolic syndrome, which is often associated with insulin resistance. This condition can lead to increased uric acid production and decreased urine pH, promoting uric acid stone formation.

Dietary Factors: High dietary intake of animal proteins, sodium, and sugar can increase the risk of uric acid stones by increasing uric acid production, urinary sodium, and decreasing urine pH.
Low Urine Volume: Although the patient's 24-hour urine volume is 2.1 L, which is relatively adequate, it may not be sufficient to prevent stone formation, especially if she has a high concentration of stone-forming substances in her urine.
Gout: The presence of uric acid stones and elevated urinary uric acid excretion suggests possible gout, although the absence of joint symptoms does not rule out this diagnosis.

Primary Hyperparathyroidism: Although the patient's urinary calcium is not markedly elevated, primary hyperparathyroidism can cause an increase in urinary calcium and promote stone formation. This diagnosis is crucial to consider due to its potential for significant morbidity if left untreated.
Distal Renal Tubular Acidosis (RTA): Type 1 RTA can cause a persistently high urine pH, but in this case, the urine pH is 5.5, which is not suggestive of this condition. However, other forms of RTA or incomplete RTA could be considered, especially if there are other electrolyte imbalances.

Lesch-Nyhan Syndrome: This rare genetic disorder is characterized by excessive uric acid production, but it typically presents with more severe symptoms, including intellectual disability, self-mutilation, and gouty arthritis, which are not mentioned in the scenario.
Tumor Lysis Syndrome: Although rare, this condition can cause excessive uric acid production, but it is typically associated with malignancies and more severe clinical presentations, which are not indicated in this case.