Well, the good news is that Darcy is not a Cornish Cross. She's a White Rock. A Cornish Cross that had been given free feed by this age would already be too heavy for it's legs, and would be spending most of it's time rubbing it's stomach feathers off by sitting, and getting it's tail filthy by not moving after evacuating it's bowels. They're not easily mistaken for other breeds by that point, and are well on their way to slowly suffocating themselves to death under their own weight.
I personally think Cornish Crosses are a terrible thing, and a violation of humanity's responsibility towards stewardship of animals. I will get meat birds at some point when I get more land, but they will be birds that can walk, forage, grow feathers, and enjoy their existance, rather than just edure existing while sitting in their own waste.
Along those lines, I would very much urge you to please really think about your position as steward to your animals. It means taking responsibility for making hard choices that they can't make for themselves when they suffer. Making statements like "I would never kill an animal, ever", is saddening. Please take your animals to a vet to perform acts of mercy, if you can't yourself. Like I said, life isn't about just eduring your existance. If the circumstances are extreme, and all the cards are played, the fine line of cruelty is a hard one to avoid walking by inaction when you have the power to make things right.
Please don't take the above as a criticism, but rather as heartfelt outreach by someone who cries over kittens that are so cute they tug my heartstrings. I love animals deeply, and salute others that do as well. But I also know that my love can blind me at times, and my ownership of animals can't always be about fun for myself. They're more important than my fun or comfort.