introducing new hen/meat bird

So a chicken at fair escaped the meat truck and hid oit on the fair grounds for a couple of weeks. My uncle took her home and asked if i wantes to take her because if i didnt ahe would be brought back to rhe alaughter house. I already have six 30 week old hens but i dont know how they would react to the new 30 week old 13 pound bird. since she is a meat bird and is already tripple thw weight of my other hens do you think she would thrive living with them and laying eggs? But to be completely honest I don't even know if ahe will fit in the nesting box hahaha. Will she keep rapidly gaining weight and then not be able to walk like I see other meat bird? I want her to live a happy stress free life but i dont want her to keep gaining weight and die a short life. What should i do? And tips on introducing her to my hens? And meat bird info i should know? Thank you!.