Although overall I think Sage has the best expressions. She's simply irresistible:
Wait, you left out my favorite Sage look!
You can sleep with her while wearing the dildo helmet and also during last party in DIKs house you can call her and tell about Cathy's leaked nudes. Other than that I think MC didn't mention it.
You'll also mention Hell Week if you wear the helmet when you go to play the guitar for her if you hadn't worn it before. Isabella knows the MC is pledging the DIKs too, and Bella tends to keep Jill up to date on the MC.
Lastly, we see the MC recount the tale of going to Bella for help after Quinn stole his clothes. I can't see how he'd get that far in the story without mentioning the chain of events that started it.*
It seems very likely Jill is at least generally aware he's pledging the DIKs, even if she doesn't know all the details.
* That said, it is odd that Jill wouldn't respond to him stealing a pair of panties. I guess the MC could have elided over the details and just said the DIKs tossed him out naked, but it seems like it would beg a question or two.