I think you've all seen.
There's always a 'showdown' of sorts, it started in season 2 with them bringing back Malin to confront Terry. Can't think of any from season 3, but in 4/5/6 we had Dani and Jack's ex, Amber and Joanna, and Shauna and Molly, all sent off alone.
The difference obviously being Ellie, Joanna and Molly had all been brought back into the villa and therefore a clearing of the air wasn't an awful idea. This with bringing Lillie back specifically even though Liam basically chose Millie seems cruel, and unnecessary, to both women.