John,
I can't count how many times a mill rep told a carpet owner to clean with nothing but cold water. The rep can say whatever comes off the top of their head, but the policy written by the mill is the actual warranty. You should ask the mill to send you the warranty and cleaning recommendations, and then ask the rep why she would recommend something different.
You're in a bit of a tough spot, as the mill rep is either ignorant and bull-headed about it, or she's trying to hide a lousy installation. If you follow her guidelines, you'll have an unhappy customer and you'll get fired from the job at some point, and you might be blacklisted by government service buyers because they think you're a lousy cleaner. You have an enemy either way if you can't find a diplomatic solution.
Of course, sometimes asking the mill a few questions can get a rep educated, or even replaced...