Offend her. Tell her you don't trust her and you need a more competent tech. It's her feelings vs your health. Since her job is to keep you healthy, and nobody is paying you to keep her happy, You can be friendly with the staff, but they are not your friends.
that happened to me once and I was sent to downtown Houston for the fistula ex-ray -there was nothing wrongmy nep doc got mad he told the unit to get someone who could cannulate me-his face got all red -- he can be a jerk but he is the best doc to get his patients what they need -the techs and nurses do not like him -- I love him -- which I always tell him when I am in the hospital under the influence of drugs I am so sorry you had such a rotten day - please do not got Wed until Monday to get dialysis it will get better
You have to have them do things your way. After all this is your body and health they are practicing medicine on.