Marguerite is in the bed faking an illness when first met.
Marguerite's shack is also a spawn point for swampfolk and smugglers, and if you fast-travel to Marguerite's Shack, they will often fight each other right in front of the shack. However, if you walk to the shack, you may end up in the middle of the fighting having both against you, since they may choose you as their priority target.
If you look a little southeast (left) from the back porch, there are some odd little straw dolls hanging from the tree over the swamp with several more on a stick in the middle of the water.
Although the map marker is called Marguerite's shack, the door reads "Open Storm Door to Moonshiner's Shack", when looked at.
This shack is one of the only locations that features cabinets with opening doors.