BaileyC, I understand where you are coming from with the OD theory, but I think the cover up done by DS is way too elaborate.
If she truly did die purely from intoxication he would know that. He would know she had no blunt force trauma, he would know she had no sharp force trauma, he would know she didn't suffocate due to lack of air alone (vs aspiration). Happens all day every day in KY. He knows that. Waking up to a dead girl in his bed would freak him out for sure - I think he would have called his two friends, maybe called his parents, called his siblings, called his best friend, hid his drugs, lots of things but bind her up and bury her and lie for 6 months! All just IMO, of course, but I will be shocked if he did all that over an OD.
Unless that OD is on a date rate drug - which would therefore be murder and a reason t0 hide a body.