Game Bird mix usually build high energy as that feed designed for game birds maybe she can't tolerate that much high energy
I've read that when hen hatch eggs it takes so much energy ..
My condolence with u :hugs
I feel for her an you buddy :hugs
I can understand your loss and m sorry for it
Well, heart attack can be a reason after I read your words like she lay down and go in her forever sleep
Happens mostly with hens who are heavyweight breeds or on high energy feed
What u feed her?
I suspect...