Salvation (Sheriff Whitehorse)
Get this one from Whitehorse himself, after liberating Hope County Jail.
Head to the Misery, on the north shore of Rock Bass Lake.
Scan the place thoroughly before moving in- one hostage is on the east end of the structure, second floor, another is on the 'ground' floor to the west. The last is in a cage dangling over the water- you'll want to leave this one for last. Note that this is not officially an outpost, but it does have an alarm system.
The zipline in from the northwest is surprisingly stealthy, and puts you right by that second hostage.
Still, just this once you'll want to clear the local hostiles before releasing the prisoners. Quarters are so cramped here that a freed hostage almost immediately alerts the baddies, which branches the mission.
Best bet is to clear the hostiles before freeing the captives. Get the two on the trawler first, then hit the red-light switch on the upper level, back of the boat, to free the third.
If you free the hostages and clear the complex silently, then your target rolls up front in a car, and can assassinated normally. If you are spotted, the target will appear in a turret boast, flanked by other turret boats.
You can snipe her right out of the water if you get a good angle, otherwise the mounted guns on the back of the Misery can be used to chew her apart.
Either way, her death completes the mission.