Just to be clear - Rya was only coming to the drop off, she was NOT be handed over, right?
Assuming this is true, Fixer would tell her to stay in the vehicle. He would grab her arm if she had a weapon. He doesn't want her out there to cause trouble.
If she is supposed to go with to the meeting - in other words all the way to the drop off and meet the other guys, then he wouldn't stop her. He would just warn the others of a weapon if he sees one.