This is a great question because Nick calls her dishonest not just once but twice. In the end of chapter three, he says of her:

"She was incurably dishonest. She wasn't able to endure being at a disadvantage and, given this unwillingness, I suppose she had begun dealing in subterfuges when she was very young... It made no difference to me. Dishonesty in a woman is a thing you never blame deeply."

Nick's discussion of her suggests that lies are regular for her. How that is defined and how much of it we actually see is up for debate.

By chapter 7, when Tom figures out Gatsby and Daisy are having an affair, he accuses both Nick and Jordan of keeping the information from him which demonstrates that type of lie that is just not telling the whole truth.

Jordan is certainly careless with driving and she acknowledges that to Nick a couple of times throughout the text. It seems that she is the type of person who would not stop to check if she caused an accident. This is certainly deceptive.

Other than that, her dishonesty is kept out of the storyline. We do not discover all her lies, but we do see Gatsby's. Perhaps this portion of the text is put in place just to get us thinking about the fact that people lie.