I am sorry about your chick. Sounds like she is over heating. What temp is the brooder at? You should have started out at between 90 and 95 degrees for week old babies and lowered the heat by 5 degrees each week for 6 weeks. Make sure you have enough room in the brooder, at least 1/2 to 1 square foot per bird in the brooder so they are not cramped in. Keep the food and water off to one side, the heat lamp on the other side. This way there are cool spots in the brooder for them to cool off. You don't want the entire brooder at this high temp. And do not cover your brooder with anything but a screen or wire for good heat and oxygen exchange.