Unprotected Sex, No Penetration, Vaginal Bleeding, Adnexal Cyst. Go For Laparotomy?

here is the issue, a virgin who has committed non penetrative but un protected sexual intercourse, now presented to the clinic for vaginal bleeding ,she has positive urine hCG test and u/s result showing left adnexal simple cyst other wise, no lower abdominal pain.
it was not possible to determine serial serum B hCG. So, can we know the sensitivity of this finding for ectopic pregnancy so that she will be benefited from laparotomy?