I would tell the parents that naps are a requirement (at least quiet time in the playpen), so if they could move her bedtime up an hour or so that would be great. 6pm! Really?! That is crazy! They barely see her at all! And then, I would let her cry it out until she understands that there is no getting out of naps. I have a couple who don't nap well at home, but they do for me because I don't give them a choice...their parents are jealous as they would love them to nap more, but they struggle. I just keep going back and lying them down if they wake up early...gradually they get it and sleep longer and longer. I could not do this job without naptime!