Clearly the cats and the home have fleas, something your daughter is in denial about. Her denial may not be entirely dishonest because after a while humans do not react as much to the bites and itching may be quite minimal. I once took over a house that was infested with cat fleas, it took a couple of weeks to kill them all off. Pet owners' denial about the pests and other health risks that pets harbour is widespread and aggressively expressed. You have an uphill fight and simply must decide whether to stick to the facts or give in to the denial/ignorance.