This x 1,000!
Do not for one second think your little meant to harm them. Children don't process cause and effect as we do. Especially at 4. I have a 5 year old daughter. She too loves to pick her chickens up and tote them around and is constantly trying to put them on or in things where they shouldn't be. She doesn't understand that life can be fragile or that stuffing a chicken in her coat as if she's a momma kangaroo could smother the poor "joey". She's just loving her chickens and playing with them.
That's where we as parents step in and make it a learning experience. "I know that you love your Nilla, but she won't be able to breathe in your coat. It's okay to pick her up and hold her, give her a quick hug, then put her down. She needs her own space." Teach your little how to properly pick them up and hold them. Teach her about stress and how chickens get stressed out easily. I use that as a tool for all animals with my children. It sounds quite silly, but once they understand, it works. "Don't do X,Y,Z because it will stress so-and-so out. You know what could happen if they get too stressed." (I tell them that when animals get too scared (stressed) they can die.) My kids love all animals and have learned to respect them this way. Takes a lot of trial and error, but eventually they understand and become more open to seeing potential danger in what they do with them.
Hope that made sense. It was sort of hard to explain haha.
Big hugs momma. Until she understands, you've got to have eyes on all sides of your head. Pretty sure I still have all those eyes. Just finally don't need them quite as much.