No way to know for sure. Her prints should have been on the blinds. If the prints were smudged that would indicate someone trying to cover up evidence. If no prints were found that could be a sure sign of crime scene staging.
Sherrill had a clear shot of backing out of the carport. Now if she were to drive out west from the house that would explain the probability that Suzie wanted to leave room for Sherrill. However, I believe that Stacy’s car would have prevented her from merely driving out on the west side. Sherrill could have pulled up alongside Suzie’s car, then backed up so as to be able to drive out with her having full view of Delmar. If she backed out of the car port she would have had to look around for on-coming traffic. This was before the era of back-up cameras and side radar warning systems found on many modern cars.
It is plausible that Suzie simply had a poor sense of direction or merely was in a hurry. If, as some reports indicated the direction of the cars differed that might indicate the perp or perps moved the cars. In that event it would have been necessary to dig around in the purses for the keys. That would likely had let skin cells slough off as most any woman’s purse is impossible for a male to rummage through. In any event it should be explained somehow. I am torn about the perp being in the house prior to the girl’s arrival. I guess it is possible that Sherrill was with a “friend” and the girls simply were interested in getting sleep. And then the perp waited for reinforcements at which time Suzie cracked the blinds.
If someone else parked the cars, there should have been some evidence that the killers wiped the cars down unless latex gloves were used. Nevertheless, that would have been necessary to find the keys. That may explain why the purses were found together in the steps to Suzie’s bedroom.