No, it doesn't mean no rigor mortis was present, it means it wasn't fully 'set' yet. RM is a gradual process, and the time it takes to fully set in depends on many factors. It is not the case that a body is floppy one minute, and stiff as a board the next.
Rigor mortis begins as soon as the heart stops.Because Sheila was slightly built,I would estimate that her limbs would have stiffened within 2 hours,,,and especially due to her activity and the assimilation of lactic acid that she used in being active.Livor would be about 8 hours where it would have shown a marked difference in her colour.