My view is that if you are suffering like now because of your worried she is not cared for, your worry will not go away. You will do what you need to do to live with/be at peace yourself.
Keep in mind that when you do bring her back, you will have a lot of work to settle her back in and work on her bullying issue. Because she has been out with a large flock, you will also need to consider quarantine her so that she does not bring any ill health to your current flock.
I wish you all the best and my heart goes to you and your hen.

I was in your situation and I worried for a whole month, I woke up at night worried about the rooster I gave away, I prayed for him during the night, during the day for the whole month that I gave him away. I felt something was not right. I took him back home and he was very sick, they did not care for him. But I was happy that he was home and so was he.