The main question is, what does Ian feel? Is he really in love with Cindy, or is simply lusting over her and feels fun talking to? I don't think either of them have deep feelings for each other, they seem like teenagers who are only discovering attraction for each other. But if Ian's attraction is more physical, Cindy's attraction is more emotional but I'd say is equal in intensity. She's not the one to fuck without some level of connection. Ian encourages her to do what she loves and appreciates her when Wade doesn't, and is himself an artistically-inclined person that she respects and seems to even be a little jealous of, she likes how passionate Ian is in pursuit of his goals and I think that rubbed off on her, making her pursue her modeling hobby with equal passion. Even her lust for Axel (that she tries to suppress) is fueled by admiration for his work and new satisfaction he can give her, not sexually but emotionally / professionally. After all he's her key to a life full of excitements where she can do something she enjoys and is naturally good at, receiving intoxicating praise all the time, opposed to distracted and grumpy Wade who is never happy with her ideas and unlike Ian is too jealous to fully trust her with her newfound passion.
But that partnership works for her as long as Ian pleases her. We can see how quickly she can explode and ditch him if he does something that pisses her off, like agreeing with Wade or trying to be controlling / over-protective, impairing that emotional attraction. Also, her attraction to people is additionally fueled by her dissatisfaction with others. She gets attracted to Ian so quickly due to her poor relationship with Wade, and in turn gets even more attracted to Axel if Ian does something to annoy her. I guess we'll see her true feelings for Ian once she breaks up with Wade and won't feel the need to constantly rebel against him.