Yeah, I hear ya I don't have a flag either. Lane position may help. When your front tire is slightly in front of her Rt mirror, she should be able to see you without dropping her phone or whatever
If you're passing a line of traffic, you'll need to either sprint to get to that spot or be ready to do a hard stop and let them merge in.
Since you'll be slightly in front of the car, you'll need to watch for 'courtesy braking' instead. Courtesy braking is when they motion an oncoming car to turn in front of them/you. Of course the turning car has no clue that you're there!