A 29-year-old woman presents at 7 weeks gestation with lower abdominal pain and light vaginal bleeding. Her β-hCG level is 3000 IU/L, and transvaginal ultrasound shows no intrauterine pregnancy and a 2.5 cm adnexal mass with minimal free fluid. She is haemodynamically stable. According to SOGC guidance, which management is most appropriate?