We had two cornish cross chickens last spring and summer. They are also bred as meat birds just as the broad breasted turkeys are. They go through much the same process when they mature, too. We had one that couldn't walk much while the other was still doing okay. Once they both were 12 weeks old they spent most of the time laying near the food and water and just panting, even when it was cool and comfortable out. It was as though they just couldn't keep themselves cool due to all the meat they were metabolizing. Their poop was very watery towards the end, too. We didn't know anything about meat birds, and had thought they were just a regular laying chicken, so, when they started panting a lot and not walking I researched what it was about that breed that made them both act that way. That's when I found out about meat birds and that they shouldn't have been kept that long. That they are supposed to be butchered before 12 weeks, often 6 to 8 weeks. Your turkey is probably at that point, too. It's so hard to watch them struggle, and I can relate to you wanting to find a way to keep her.
I don't honestly know if you will be able to, they are bred to metabolize so quickly and then be butchered, so, you will be working against nature, but, who knows, maybe it's doable. I guess if you are successful you will be the expert on here for others that may want to try.
I hope it works out for you.