In Eloise's reality any woman all done up - she could be a model, a ballerina, or begrudgingly, Nicki Manij - is a Barbie. She excitedly says so any time we see one in a book or on tv.
Since watching Eloise at the Plaza a dozen times now she has also decided that any man in a suit must is a Prince. Makes sense to me.
A few years ago Karl Lagerfeld did an exhibit at Colette, the extremely cool Parisian fashion retailer, featuring Barbie and model Baptiste Giabiconi as Ken. I feel this is pretty much what Eloise is imagining when she says Barbies & Princes.