First of all it won't hurt her to brood a clutch of eggs in hot weather as long as she has water available. I just had an 11 year old hen hatch 8 chicks. Your hen that died didn't die because she was broody, it's a natural process. She would have died anyway.
However, if you want to break your broody it's easy. Put her in a wire bottomed cage with nothing to sit on except the wire floor. She'll stop within a few days.
Absolutely. The best and easiest way to break a broody. If she doesn't break after being on wire off the ground with only open air under her for a week, then let her set. I have one I can't break no matter what I try so I just let her silly self sit there. But the rest will get un-broody in about 3 days in the cage. You can't let them out at all during that time or give them anything they can sit on and keep their underside warm.