I'd definitely try to do naps at home in one as well.
OR if you can find one/afford it, you could purchase a portable crib that is wooden and more like a real crib but still has the smaller dimensions of a pack n' play. They often have them in vacation spots (we'll be renting one down the shore this summer) If not, they sell thin mattresses for them that you can squeeze into a pack n' play (they are a bit narrower though and a slight tad longer so they fit a bit oddly--you may have to put something in the gap along the side from it being narrow but it can be done--just isn't the best solution) and it feels more like a real mattress and she may like that better. I did that as well and it helped.
Not sure if she naps the kids together or separately, if it resembles the room she has at home in terms of darkness/lightness and if she has HER blanket she sleeps with at home, her lovey, etc. That may help as well. Anything that "smells" like or "feels" like home makes it easier as well.