The renters would be liable only if they were negligent in leaving the bed framing lying on the driveway during what I assume was a legal yard sale.  Presumably, if the neightbor was shopping the yard sale, she understood that things at a yard sale are generally scattered about.  Also, if I were representing the renters I would argue that the bed framing was open and obvious, which cancels out liability.  Certainly the homeowner did nothing negligent by renting his home to someone who had a yard sale.  I do not think your neighbor can recover against anyone in this situation.