She had her oil along, but never got around to using it.
From a photographic standpoint, I have definite feelings about the use of oil. It definitely changes the look of the model and accentuates the "hot" areas, so far more caution is required to ensure these areas do not blow out. Using a spray bottle of water to spray an oiled up model is also something that can be extremely effective visually as the water creates beautiful hot spots, especially if the model is reclining. This technique works well when doing body sculpting shots. Models prefer using warm water is the sprayer!
When I go for the oiled look, it is usually the last sequences of the shoot, as the model has wipe down and shower to get rid of the oil. There's no easy / short way going back to the non-oiled look once it has been applied . Models tend to be paid by the job or by the hour, so shower time during the shoot is not particularly cost effective.
The other issue with oil is that it can and does drip onto the studio floor and onto props and equipment. I've never slipped and fallen on areas where oil has dripped, but have spoken with photographers who have been less lucky...