I would say Lilah doesn’t give Roo what for because she just doesn’t want to.I think you are right about the ducks gone and I don't know why they are mean to each other either but I can't help thinking there is jealousy involved.
They are not flaring their hackle feathers at all, Jellybean mostly sneaks up on Roo although Roo has gotten wise to it and often runs away. Lilah has kicked and bitten Pedro before but its rare, Pedro has kicked at Roo and pecks her too on the back of the neck but tends not to prolong it once she's got her message across she walks off from Roo. Jellybean kicks at Roo daily, she bites her, pecks her and scratches her with her claws, she hammers down on Roo's neck, head and face with her beak. Often Lilah will break up the fights she will pull the girls off Roo and sees them off by pecking them sharply but then Roo goes and steals whatever Lilah is eating and pecks poor Lilah!
It seems the ducks going has confused everyone
On this pick taken last weekend, if you look you can just about see how Roo is starting to lay on Lilah, shortly after this was taken, Roo pecked Lilah in the face, Lilah moves away but Roo moves too and ends up almost laying completely over Lilah, she pecks Lilah again and so Lilah gets up and walks away and misses out on having her dirt bath.
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I don't understand why Lilah is being submissive to Roo, nor do I understand why Lilah doesn't give Roo what for like she gives the others, unless its the mother in her and she still sees Roo as her daughter - who knows
I love Roo very much but I really believe if we only had the other three we'd have no problems at all, giving her up is not an option though.
I did have Pedro and Jellybean in the house, Pedro for 5 days, Jellybean 7 days, no changes on the pecking order then, no one forgot anyone and both strolled back in as though they had never left. The attacks calmed down somewhat but when we took the ducks the attacks escalated again.
Roo is ruining the only friendship she has which is with Lilah, Pedro and Jellybean won't ever be friends with Roo - Lilah, Pedro and Jellybean get on relatively well together, put Roo in the mix and it all goes to pot and I need a solution to this which doesn't involve re-homing any of them.
Clearly she could if she wanted.
I know it’s hard to watch because from a human standpoint it looks really mean but chicken society can be brutal.
The more we interfere the longer it takes for things to settle down.
The more we change things in their environment the longer it takes too.
Chickens hate change but they can adapt to it.
Cleo gets pecked by almost every bird in my flock.
That’s 20 birds!
But she has learned to keep her distance.
She moves fast now so they can’t get her.
She is lowest on the pecking order because she’s the youngest.
But it probably won’t always be that way.
I hope you can take a deep breath and see that they are enjoying their lives.
They can dust bathe and probably sun bathe too.
They have good food and fresh water.
They are doing great.
Don’t worry about them.
I just need to give them time to sort themselves out and readjust. When I think about it, Pedro and Jellybean were with the drakes from two weeks old and had never had a single day without them and now they are gone, and Roo hung with the ducks a lot everyday, the drakes used to protect her from the others, and Jellybean has only recently stopped looking for them. Lilah is the only one who seems unaffected by their departure but even so it is bound to have made an impact on the flock. The storms we are having aren't helping matters either, the high winds scare them as they are not used to it at all, we still keep our backdoor open for them during the storms so they can hide in here if they choose to and helps a lot but at the worst of the storms they have been showing signs of stress and I guess all these factors together puts further stress on their relationships. Here's hoping they sort it out soon 
