Ian is simply respecting Holly's agency. If she'd rather fuck him than her sweet girlfriend, who is he to question that? /sCan you mention the detail to Eva that was discussed a few pages back, about slutty Holly going to Ian's room even when the Lena romance for her has been going on?
Perhaps it's intended and that's fine of course, but I still find it curious that Ian himself wouldn't at least inquire about Lena when he was such a sweetie-cutie-wootie-pie to let them have their beach romance to themselves just a short time earlier.
(it's also really dumb to bring up one's significant other when they're slipping in your bed. We don't want them to lose their nerve and/or mood, do we.