A young woman who was orphaned as a child & raised possibly in New England is brought back to her family estate she inherited somewhere in Louisiana or similar with Spanish moss on the trees, plantation shutters on the exterior doors, etc. I believe she had received letters from her “aunt” who has lived in the mansion but who I think turns out to be just one of the caretakers pretending to be her family.
While there, the caretakers try to keep her captive without being obvious by making her think she’s going insane so they can keep the estate for themselves.
There is a sheriff from town who comes out periodically & another man, perhaps a reporter, who has become romantically attracted to her.
Someone is killed & thrown in the swamp & later found by the girl and the possible reporter as they’re trying to escape on foot.
Any suggestions as to what this movie might be are greatly appreciated!