A 48-year-old Indian woman with Type 2 diabetes and hypertension presents with recurrent transient ischaemic attacks (TIAs). Her lipid profile shows: Total cholesterol 240 mg/dL, LDL-C 140 mg/dL, HDL-C 32 mg/dL, Triglycerides 380 mg/dL. She is on metformin and amlodipine. On further questioning, her mother has diabetes and elevated triglycerides. Genetic testing reveals a heterozygous APOE2/E3 genotype and a mutation in the APOC3 gene. Which lipoprotein fraction is most likely elevated and driving her atherogenic dyslipidaemia?