Reedbrake was a community just South of the present day town of Douglas. There is still a voting beat in Marshall County called Reedbrake.
The larger cemeteries in this area which are online include Nixon Chapel and Liberty Hill. Go to USGENWEB to see these cemeteries on their Tombstone Project. From the Tombstone Project page, you can also contact Alice Beck by email. Ms Beck has surveyed a lot of cemeteries in that area and may be able to help you more.