And yet their relationship takes quite a hit if Ian accepted Holly's invitation
Well, obviously. That's why i said Cindy wouldn't resent it
too much as opposed to not resenting it at all.
You make your point well, but I disagree. How does it make sense for her to keep it together after a totally dissapointing birthday party?.
The same way it makes sense for Cindy to regret what she's done and attempt to pretend things never happened, if Cindy and Ian fuck on that day. People can act very differently when their emotions run high, and when they've had some time to cool down.
At the height of emotions Cindy is much more prone to give in to a wish to be close with someone she feels strong connection with, even if she knows this is morally wrong, than when she's got relatively cool head. Also, in the scenario where Ian
isn't there when she's most vulnerable, then this extra bond between them doesn't get to form. He remains a good friend she may have some crush on, but he's (now) also someone who, like everyone else,
wasn't there for her when she needed someone. It'd make it quite easier for Cindy to get over this crush, or at least not to act upon it in the future.
Some chances are literally once in a lifetime, and if you blow them, then that's it.