Medication-induced coagulopathy: The patient is on multiple medications, including Microgestin (a form of birth control), which can affect coagulation pathways. However, the most notable medication that could contribute to easy bruising and bleeding in this context is likely the combination of effects from various medications rather than a single agent. The presence of low iron and folate could also contribute to the clinical presentation, but the coagulation study abnormalities (PTT 35, INR 1.2, PT 12.3) suggest a coagulopathy. The medications, especially when combined, could potentially alter liver function or affect vitamin K-dependent clotting factors, although liver function is reported as normal.

Vitamin deficiencies: Low iron and folate levels can contribute to bleeding tendencies, although their primary association is with anemia and thrombocytopenia. The patient's normal hemoglobin and platelet count suggest that these deficiencies may not be the primary cause of her bleeding but could be contributing factors.
Hormonal influences: The use of Microgestin could influence coagulation pathways, but the effect is more commonly associated with an increased risk of thrombosis rather than bleeding.

Liver disease: Although liver function tests are reported as normal, liver disease can have a wide range of presentations, and coagulopathy can be an early sign. It's crucial to not miss liver disease, as it can be deadly if not addressed promptly.
Vitamin K deficiency: This could affect the production of vitamin K-dependent clotting factors, leading to an elevated INR and PT. Although the patient is on vitamin D, the question does not mention vitamin K supplementation.
Thyroid disorders: Both hypothyroidism and hyperthyroidism can affect coagulation, though this is less common. The patient's medications and presentation do not strongly suggest thyroid disease, but it remains a possibility.

Inherited coagulopathies: Conditions like von Willebrand disease or other factor deficiencies could present with easy bruising and bleeding. These are less likely given the patient's age and the fact that she has presumably undergone medical evaluations previously without such a diagnosis being made.
Bone marrow failure syndromes: These could lead to cytopenias and potentially affect coagulation, though the patient's normal WBC, hemoglobin, and platelet count make this less likely.
Autoimmune disorders: Certain autoimmune conditions, like lupus anticoagulant or antiphospholipid syndrome, could cause coagulopathy. However, these would typically be associated with other systemic symptoms and specific laboratory findings not mentioned in the scenario.