Okay so what happened is that when I went back after the “intervene” scene, she is not at tavern and I tried everything between skipping a few days to restarting the story. I don’t know what’s missing. Also I already fed Beth every time to work but she is not there still.
Ah. that's the wrong choice. Since only one sister will be left. The event can only trigger if you settle things peacefully.
When you confront Mallory in the large hunting ground area, you need to pick "Believe Eve". You'll fight Mallory and after winning, Eve will show up and then both will head back to the tavern. Then once you sleep the event can trigger.