Holden finds a lot of people 'dishonest and superficial' hence his concept of 'phonies'. A standout example is Sally Hayes who he calls 'the queen of the phonies'. Everything about her he finds false: her social interaction eg. the way when she answers the phone to him she asks who it is when her father has already told her; he finds the rituals she observes tired and cliched eg. inviting Holden over to trim the Christmas tree. She is even dishonest when it comes to enjoying yourself: she wants to go ice-skating not because she is any good but because she knows she looks good in the skirt you wear.
Holden might overlook these minor irritations, but he dismisses as phonies people he can't connect with. Despite the fact they are from the same rich background Holden can't connect with Sally at all. This is shown when he recklessly tries to get her involved in his fantasy of living away from society in a log cabin in Vermont. It's hardly surprising that she dismisses this out of hand but Holden blames it on her superficilaity and inability to have 'an intelligent conversation'.
Sally is not necessarily as superficial as Holden thinks; they are however, complete opposites: Sally is happy with and comfortable in the social environment which Holden despises.