Watched the film Obsession (great piece of work, loved it. Kudos to tht young director and the actors for pulling this off) and it gave me a terrible idea.
The Batfamily and Batsis have had a stranged relationship for years recently. Not inherently bad, Batsis still cares about them and does her part in joining dinners, hanging out when they can, and it's all very polite and fraternal enough, but she's got more independent and putting distance between them to find her own identity outside the Wayne's shadow, outside Gotham. Given she was the only not involved in crime fighting, she was obviously neglected and a bit sidelines growing up, and while that was nobody's intention, it still created a drift and the Batfam are just realising it because they're used to her doing most of the emotional work by brushing it off and accomodating to them until she grew up, did some healing and decided to draw a line at last. They all miss her, they wish things were back how they used to, with her always so close to them no matter what. Or how things when they were all younger and Batsis still looked at them with admiration and pure love.
Now she feels far away. She has her own friends, her career, her own dreams, and a life entirely built on her own and outside of her family. And she keeps drifting towards it, no longer having so much time for them. It's not the same. Her feelings are obviously not the same. And it hurts them so bad. She cares about others now and gives them what was once theirs.
OR alternative case: The relationship was always bad and Batsis always felt neglected so she grew colder towards them and now is simply gentle and polite out of cordiality, and the Batfam are now seeing her for who she is and want to be part of her life. Want her to come back to them and let them all be one happy family again (if they ever truly were).
So one of the Batfamily, haven't decided who but for now I see Tim or Damian (but just imagine whoever you see fit, because the person who does it in question doesn't matter), gets one of those One Wish Willows. Either by accident or someone gives it to them to try. They're exceptical at first, obviously, and don't really believe it works, but in a moment of impulsivity, mixed with curiosity and longing, they do it:
"I wish [Batsis] loves us more than anyone in the fucking world"
And then they snap the willow in half. Nothing feels different at first. Nothing has seemingly changed. They chastise themselves for even trying it, a bit dissapointed.
But suddenly, Batsis' attitude takes a 190 degrees turn with them. She's moving back into the manor, claiming she misses them too much to stay away. She sold her apartment even. She's openly loving and adoring with them. She's gotten clingy too, perhaps a little too much, but the Batfamily are all so happy! She loves them. They're not losing her. They have fun together again and she smiles brightly at them, laughs with them, goes along with whatever they say with a smile that sometimes seems like it's pulling her skin
But as time passes, her behaviour gets more...irrational. Weird. Creepy. The Batfamily began to realise something is wrong with her. Whoever made the wish knows. She's also weirdly possessive and jealous too, wanting their attention all to herself and throwing tantrums when they ignore her or simply don't go along with the invisible script she's following now. It gets to the point she injures herself even on some of her breakdowns, cries and begs and screams.
The one who make the wish eventually comes to this awful realization, and so does the rest of them...
Their sister is trapped somewhere within her own body.
And the worst part is...they're not as eager to fix this as they should, because when she's well, she's back to being all over them and devoted and compliant. And they're selfish.