Once you receive her message, head to Hot Springs and talk to Tucker to start this mission. Fast-Travel to Marion Forks and head towards the Old Wagon Hotel where you’ll find several armed men holed up in the building.
Sneak around the building and enter it from behind. Take out the hostiles using any method you want. You can also enter through the second floor window using the junction box outside to Boost you up. Once all enemies are killed, free the hostage on the second floor porch to complete the mission.