Location assist by the most advanced of Techies. Cell twr and ip or cell no. triangul

Ok, so try and stay with me on this... I just got word about a family member that has gone missing. I've been doing some investigating and it sounds like she got in with some seriously shady business people from the other side of the border and now has gone missing with calls being made to the fam with threats. Last year I found my friends location using his cell number and a couple sides and an app that no longer is being offered. He was pin-pointed with 10 feet accuracy. I've tried all of the sites and other avenues I know, but haven't been able to get any foot on it. I know the reason is because its an Mex cell number, BUT I know that wherever she is, it cannot be more than 7 miles away from the Mex/American border. I am at my witts end and am desperately seeking any help or advice possible. The cops and other authorities are useless and would rather wait for something tragic to happen before they make a move. I cannot do this. Any help, advice or wisdom would greatly be appreciated and swift results will be compensated.

Thank you for your time,
SNL