Look for a half marathon clinic or training group working towards the same race if it is local. Running stores will be able to point you in the direction of a few. I am not familiar with these specific ones below, but they came up with a quick google as examples:
https://www.fleetfeet.com/s/dc/training
https://www.dcroadrunners.org/training/10mile-half.html (this one has closed because they are working towards the March RnR race, but this type of group is what you want)
A coach or trainer will not be very good value for a first half marathon. I'd instead recommend picking an appropriate Hal Higdon plan based on the weekly mileage they were already doing, and find a local free running club to run with 1-2 days per week that fits within the plan.