Get a large bendable straw and slit it up the side. Fit the straw over the leg with the bendable part over the knee and tape it on with vet wrap or something that will let the leg breathe. Don't let the edges of the straw dig into it's leg. Hopefully you can find a straw big enough. This has worked for me on various small animals. You may want to put an antibacterial ointment on the open sore area. My animal casts usually stay of for about two weeks before I remove them,
just take 2 smalls tooth picks and place in both side of the leg the tape it with bandge tape its white and let it mend on it own leave it like that for a least a week and try to keep it from moving so much like in a tank so borrer
With the bone protruding through the skin, I'm afraid you're going to need vet assistance to replace it or you'll have to put her down to end the suffering. I also hope someone comes along with more experience, but this does not seem good at all. I'm sorry.
My three week old chick was stepped on by my horse at a few days old. Broke the right leg and left foot. It's right leg had a compound fracture ( bone sticking thru the skin). It broke right at the hock making the lower leg unmanageable. I took the chick into our home to care for it since it's mother didn't. I wrapped the joint with a small piece of vet wrap. It sticks to it's self, not the skin, to stabilize the break. It hopped around on the one leg. Was doing very well. So much so, that I removed the vet wrap and he was able to walk and scratch. Then a few days later it rebroke the leg flying out & landing on that injured leg. So now I'm starting all over again. BUT the chick is eating, drinking and doing all the normal things. I've kept it warm and well fed. It's like a member of the family now.
I agree that if the bone is protruding, you need to get her to the vet asap. If it (bone) is exposed too long, you can get alot of infection. I don't know if it can be closed at this point and sutured due to it being open for more than 24 hrs. But, ask your vet. I recently had a chick that I rescued from the farm store with a fractured leg and infection at the joint. The bone had deteriorated and I did have the leg amputated. The chick is doing quite well, but needs to be kept on a blanket in a cage and with only one mild mannered friend for a long while. She/he will also need to be kept in a protected area when she goes outside, I have an aviary and only let them range when I am nearby so decided to try to keep her going. Good luck.