The only way to remove roll marks without steam would be to ignore them until normal traffic pounds them down, or pull the carpet so hot water could be used off-site. A pile lifter would work until they walked on the carpet next.
With a little more information you might have been able to find out where she got the no-water information and re-educate her. In hindsight you could agree that elevated moisture over several days can contribute to mold growth, but the process of removing roll crush and normal cleaning will both require the use of water, and in both cases the carpet will dry far too quickly to allow any mold growth. The person that told her no water is likely not a carpet cleaner, and should probably get a call just to get a heads-up that he's been misinformed.
The real answer could be that she either misunderstood a complex conversation and chopped it into simple bits, or got the information from a friend, Chem-Dry ad, or Oprah Magazine.