Do we know if she was strangled first. then hit or not? My thinking is, that if it was accident that was covered up, the accident couldn't have been the garrote. So if the garrote was first I find an accident to be unlikely.
The head bash was not an accident, neither was it intended to kill her. If she was bashed to shut her up (a scream was heard by a neighbor around midnight), the scream likely followed a sexual assault forceful enough to cause her to bleed from the vagina. I for one, do NOT believe the head bash was done to stage the body. There WERE some signs that she was still alive when bashed- one being the mild swelling found in the brain (noted in the autopsy as mild flattening and narrowing of the sulci and gyri- the lobes and spaced between them). This does not occur in a dead body. There was also bleeding in the subdural space- also does not occur in a dead body. Most experts and LE studying the case agree the head bash came first. I agree.