Originally Posted by
eastindywalrus
Ouch. Rough itinerary.
I can't answer your question here, unfortunately. I will say that 18 hours at AMS, even in a lounge, is a hell I've endured three times. The first time was miserable. The second time I found one of those relaxing chairs near the upstairs food court to doze in, and it was still about 90% as miserable. The third time I did the smart thing and forked over the cash for a room at the Schipol Yotel. While I don't know if your niece is travelling for school and/or is on a tight budget, but $115 is a small price to pay for a place to doze, use the restroom, shower, and in general get away from everyone else while still being on the right side of security. It looks like some days/nights are available beginning at $62 too, which is obviously much more palatable of a price. Throw in a few bucks for some airport food (which will, as you indicated, easily beat the quality of the lounge offerings), and binge some Netflix or something to pass the time in a nice, air-conditioned bed.
I can concur, Yotel at Schiphol is excellent and a reasonably affordable alternative to any lounge situation. As far as I know, the 30-day pass was done away with 2 or 3 years ago.
Why limit yourself to the airport though? Depending on how much energy your niece has after her trip, she could also easily spend an afternoon in Amsterdam, it is very easy getting there by train and fairly cheap, too. The train takes you right to the city center. What I like to do when I have a longish layover is renting a bike near Centraal and getting some exercise while enjoying the beauty of the city. The options, of course are endless. She could also potentially get a hostel bed somewhere in the city, if she decides to go, which could potentially be more convenient and even cheaper than the Yotel!