Sorry for your loss.
Trimming their wings is a good idea.
You need to provide protection for chickens especially a coop at night.
You can train chickens but first it takes work on your part.
If you’d like to teach your children a different lesson other than chickens are prey to just about everything then start anew.
It not too late to do something.
A lot of people think like your boyfriend....thinking that a hawk just swoops in and carry’s the bird away. A VERY large raptor could yes...Eagles for example.
The truth is they will kill them on the ground. Younger inexperienced hunters leave a lot of walking wounded chickens.
You must take action if you want a different outcome for your flock. It’s only a matter of time till the next predator kills one.
Or if there’s just something inside you that feels they need to be free then advice is a moot issue.
I don’t mean to sound harsh
But circumstances and consequences will not change until you change them. Best wishes
Trimming their wings is a good idea.
You need to provide protection for chickens especially a coop at night.
You can train chickens but first it takes work on your part.
If you’d like to teach your children a different lesson other than chickens are prey to just about everything then start anew.
It not too late to do something.
A lot of people think like your boyfriend....thinking that a hawk just swoops in and carry’s the bird away. A VERY large raptor could yes...Eagles for example.
The truth is they will kill them on the ground. Younger inexperienced hunters leave a lot of walking wounded chickens.
You must take action if you want a different outcome for your flock. It’s only a matter of time till the next predator kills one.
Or if there’s just something inside you that feels they need to be free then advice is a moot issue.
I don’t mean to sound harsh
But circumstances and consequences will not change until you change them. Best wishes
Hens go broody when you don’t want them to… and won’t go broody when you do. 
I think she was separated from the flock (which is typical like I said they don’t get along) and was just at the wrong place at the wrong time.