X <-- Cindy Starts here and then...
...Ends way over here --> X
We like to call this a journey. If Ian continues to feed her self-centeredness and ego the journey is a much shorter and she ends up much like the women shes modeling with. Shallow, vain, self-centered, and cutthroat. If Ian loves her and is clear about his boundaries with her, Cindy realizes that she has been a bit of a brat and starts to open up much more with Ian about her worries and fears, about her feelings towards Ian, and how she feels others perceive her. If Ian has helped Cindy and Wade find middle ground, Cindy show remorse that they broke up and will probably have a heart to heart with Wade later. It might not save the relationship, but it's still a sign of growth from where they were at, at the beginning of the game.
It's been obvious for a long time that Cindy wants to be a creative person in a similar fashion to Ian, Lena, and Holly. We see that desire manifest in the form of her jealousy of Lena and her curiosity about Ian's writting at the art gallery. Modeling was an easy path for her, because of her natural beauty. Unless Ian feeds her ego, she comes to the realization that modeling is ephemeral and that she isn't being a truly creative person like those previously mentioned. Where her journey goes from that moment of realization, we don't yet know, but she keeps taking that next step forward.