Bread, Age, Gender?

[Weeg]

Thanks for the tag @Silkie Princess
OP, yes it does look like you have a Cornish X. I wrote an article about my learning curb in raising Doodle and Smudge, by Cornish X pets. You do need to restrict feed and have her either separated (to keep her away from the free choice feed the other birds are eating) or make the feeder inaccessible to her in one way or another.
I also have a thread with TONS of info, I'll link that here. You can find my article on my profile in the articles section.

 

[Weeg]

Here's my thread. If you have any other questions feel free to ask me. I think you'll find a lot of the info in this link- https://www.backyardchickens.com/threads/experimenting-with-a-few-meat-birds-as-pets.1449592/

 

[Weeg]

Thank you! They’re currently on purina start and grow crumbles and she does seem to eat more than the other two but still stopped eating better the food was gone. They haven’t had treats yet and get to free range during.

Can you feel her keel bone? Its the bone that runs down the middle of there body. You can usually feel it in between the legs. Grab one of your other birds and feel their keel, then grab your Cornish X and feel her keel. It should be somewhat prominent and sharp. I wouldn't be surprised if you found it hard to find since no feed has been restricted. As long as she's still mobile, you should be able to get her weight back down though. I know I had to with a crazy dare devil like Smudge! She'd so anything to get into a feed bag.

 

[Weeg]

I do recommend free ranging often and making sure she is at a healthy weight. @Weeg may know more about a restricted diet.

This is very important. Freer raging gives them the option to forage, and feeding a small amount of feed in the morning scattered in the bushes is a great way to encourage foraging. I talk about this a lot in my article I'll find that and link it here for ease.
Thanks for the tag @cherrynberry!

 

[Weeg]

Heres my article- https://www.backyardchickens.com/ar...ge-my-adventure-with-cornish-x-as-pets.76727/
Hopefully you find it helpful.

 

[TheOddOneOut]

I’m pretty sure they were bought from tractor supply with no means of proper housing/care so they ended up with us now that the weather is getting colder. So with it being a meat bird, can’t we still just keep her as part of the flock?

She will likely suffer major health issues throughout her (short) life.

 

[Weeg]

She will likely suffer major health issues throughout her (short) life.

Not necessarily. If OP can get her weight down, keep her active and on a low protein feed than its likley that she can have a short, but happy life. I know that Doodle is.
If OP didn't restrict feed, wasn't able to get her weight down, or even if she did everything right this hen went down hill, then you're absolutely correct. Just saying that Cornish she does have a chance at a happy life.

 

[Girlmomx3]

We still have them in the empty coop but they’ve been free ranging well with the Muscovies. I often give the Muscovies lettuce or shredded carrots. Should I not give them any when she’s out with them?

 

[bruceha2000]

Since there is little in the way of calories in lettuce or carrots I wonder if her eating them to fill up wouldn't actually be a good thing. Assuming she will eat them ... my chickens are not interested in such things. They do like apples, tomatoes, melon rind (right down to a paper thin shell).

 

[Weeg]

I've heard that kale, and spinach are good snacks for Cornish since there are little carries, and it helps them feel more full without getting them fat. Avoid any commercial treat such as mealworms and cracked corn though.