24 hours after attack and flock won't let chicken back in

[LadyBrenSirMike]

Yesterday something got into our pen and attacked two of the hens. The one that survived, Merida, was at the top of the pecking order. We kept her in for the night to monitor her.
She's lost feathers but other than that there are no other injuries. We tried putting her back with the two unaffected hens and the immediately started pecking her, she didn't fight back.
We currently have her in their old dogcrate/pen and placed it right next to the the side where the food is for the other hens, so she is protected.
How long should it take for them to accept her? Should we try it one on one instead of two on one? Should we try it every day? Is it better to try in the morning rather than at night? Right now is when they usually head in to pick their spot for the night and Carlotta, the barred rock, keeps returning to Merida almost wondering why she isn't following routine.

Thank you so much
I'll admit this has me concerned for when we introduce the itty bitties (who are 2 months younger than these 3) into the flock!

 

[ten chicks]

Yesterday something got into our pen and attacked two of the hens. The one that survived, Merida, was at the top of the pecking order. We kept her in for the night to monitor her.
She's lost feathers but other than that there are no other injuries. We tried putting her back with the two unaffected hens and the immediately started pecking her, she didn't fight back.
We currently have her in their old dogcrate/pen and placed it right next to the the side where the food is for the other hens, so she is protected.
How long should it take for them to accept her? Should we try it one on one instead of two on one? Should we try it every day? Is it better to try in the morning rather than at night? Right now is when they usually head in to pick their spot for the night and Carlotta, the barred rock, keeps returning to Merida almost wondering why she isn't following routine.

Thank you so much
I'll admit this has me concerned for when we introduce the itty bitties (who are 2 months younger than these 3) into the flock!

Try putting another hen with her,then reintroduce the two together. She probably isn't reacting because she has suffered a traumatic event,chickens do not handle stress at all,may take her a couple of days to return to her normal self. She is probably still terrified.