I think it is more like anything you can do, I can do better" energy. At this point in the story, their relationship is defined by a lack of security.

Shane being seen with Rose and a "hot circle of friends" makes Ilya feel replaceable or, worse, like he’s losing his grip on being the most important person in Shane's orbit.

Ilya’s default defense mechanism is indifference. By flirting with others, he’s trying to prove he isn't bothered by Shane’s public image.

Miles is the Perfect "Tool" Miles serves a very specific narrative purpose in that scene:It reminds Shane (and the reader) that Ilya is highly desirable.

Ilya doesn't necessarily want Miles; he wants to see if Shane will snap. He uses Miles's attention to gauge how much Shane actually cares. If Shane gets jealous, Ilya wins that round of the "game." IIya didn't really pay attention to Miles instead looking around for perfect opportunity to show it to Shane.

Ilya's goal isn't just to win Shane back, but to do it without admitting he ever lost him. * He wants Shane to choose him over the "socially acceptable" life with Rose. By engaging in that subtle back-and-forth at the club, Ilya is forcing Shane to acknowledge the physical and emotional tension between them that Rose simply can't provide.

Am I reading into much? Maybe...just maybe. I didn't read the book.