They found her body 4 1/2 days after she disappeared. I'm not sure whether she was killed right away or not, but from the articles I read from back then, they said there was quite a bit of decomp.
"Quite a bit" would likely be an understatement
Her body was left to stew in summer heat for almost five days, I can tell from very recent personal experience that there was likely not much left of her at that point and what was left was not pretty to look at.
An elderly man who was living alone in an apartment complex owned by my father passed away in his sleep somewhere around last August 10. He was a very quiet fellow who kept to himself, had his groceries delivered and rarely ventured out. According to other tenants he may have had about 5 visitors during the 20-odd years he'd been living there and had no known family, in fact his body is still in a fridge at the Coroner's, unclaimed. He wasn't poor or anything (bank account balance was well into the six-figures), just a bit of a hermit, an eccentric. Because of his reclusive lifestyle no one noticed anything was wrong until a horrid stench started to waft out of his balcony door which had been left open. I was the one who had the unpleasant task of checking on him and what I saw in his room well, I'm not about to forget. This happened in the middle of the summer's worst heatwave and his AC was off... heat inside was oppressive, the stench was foulest smell I have ever been exposed to (I threw up, it was a gut reaction). The body was bloated, blackened, putrid and crawling with maggots, thanks to the open door. Hundreds of flies and wasps were flying about the room.
The body looked nothing like the man had when he was alive and I doubt that Mary Jane Reed's was in any better shape. There is no way a funeral director could have redressed her so the fact that she was buried in the clothes she was wearing is perfectly understandable. Like others have said the most likely scenario is that the funeral director didn't have the heart to tell the family about the shape of the corpse and accepted the new clothes. It was obviously a case of closed casket funeral so no one would know, and they put the clothes in the vault along with the casket. Perhaps wrapping them in newsprint was a bit odd but since they thought no one would ever see them again it was no big deal.
There are plenty of oddities with this case but the clothes in the vault, at least, are easy to explain.
