A 45-year-old woman attends her GP surgery requesting emergency contraception. She had unprotected sexual intercourse (UPSI) 80 hours ago. Her last menstrual period (LMP) was 12 days ago, and her cycles are regular (28 days). She has no contraindications to any method. According to Faculty of Sexual and Reproductive Healthcare (FSRH) guidelines, what is the most effective method of emergency contraception she can be offered now?