Introducing the new girl to the established flock

I have 6 older girls they are 5 months and I have a 2 1/2 month old Polish chicken who is the sweetest chicken ever. I was at my friends parents farm and this chick followed me all over the farm and when I picked her up and she fell asleep in my arms. then I put her down so I can eat dinner and she fell asleep on my shoes so they told me I could take her home. So I did and I put her in the cage with the older girls and they attacked her. So I put her in a dog kennel in the coop and she is around them all the time. but the older girls seem to still try and peck at her thru the cage. Im not sure how to get them to all play nice?? Help me.