Cathy is getting married to Andy, yes.
Considering Liam openly joked about the "surprise" being Nathalie during the GW event of v.115, something like that could easily happen during the Cathy event of this update. And with enough Lesbian Temptation points, Sophia wouldn't need to be absent for anything to happen between Liam and Cathy. Cathy might even approach Sophia directly, which would mean that Liam isn't cheating on Sophia, since we know he wont in the game.
I believe the next event with Jules is on Playable Day 16, which is why I suggested Christine. But I doubt anything interesting is going to happen between Ellie and her friend during a Sam event. When the Ellie branches start on Playable Day 16, that's an entirely different matter.