Built a real smoke house over 4 decades ago. About 6' X 6' square. Had a bury stove pipe, about 1' deep, run to a little fire pit (hole in the ground) about 14' away from the house. Worked great.
Doesn't have to be clay, but that would work. A lot of families had smoke houses in the small town. They mostly used about 5-6" dia. galvanized stove pipe. Just dug a ditch about 1' deep, maybe a little, lay the stove pipe and cover with the dug out dirt. Oh yeah, the end of the pipe had an elbow and is in the center of the smoke house.
Don't think she knows anything about it. She's going to be taken in, charged, and not be let out on bail. Maybe even military court.