This thread may help you break her. There are several different ways suggested, but I favor the wire cage.
Break a Broody Thread
https://www.backyardchickens.com/forum/viewtopic.php?pid=2176186#p2176186
How will the other hens react to a baby chick? Nobody knows. Each chicken has its own individual personality and will react in its own way. Hens have been raising chicks with the flock for thousands of years. Sometimes it goes without a problem and sometimes there are disasters. Some of the things I think are critical are the personality of your broody, the personality of the other hens, and how much space you have.
Most broodies are very protective of their chicks. They have a real bad attitude and don't hesitate to wade into any other hen or rooster that is a threat to their chicks and teach them that these chicks are to be left alone. But not all broodies are that way. For whatever reason, some do not protect their chicks. You really cannot tell how your broody will act until she is in that position. Some of the meekest, mildest hens can become extremely ferocious when their chicks are threatened, but some don't.
Some flocks have chickens in them that seek out and destroy any weaker chick or chicken. Most don't and Mama will usually change the mindset of most of those, but there are some that are just relentless. It is usually hens, not roosters, but it can be either.
If Mama has enough room to work with, she will normally keep her chicks separated a bit from the rest of the flock. Not necessarily in total isolation, but on the outskirts so there are fewer chances for conflict. If space is tight, Mama might not be able to keep them out of harms way.
I can't tell you how yours will react. I let my broodies raise chicks with the flock and really don't have any problems, but then I have a lot of room.
Hope this helps a bit. Good luck!!!
