First, please calm down. It may be nothing. Mine return from a day of freeranging with huge hard crops every night. It means they ate a lot that day.
I don't mean to sound condesending but you do know that's called a "crop" and that's where they store their food? If not, welcome to chicken anatomy. I'm guessing, since you called it a "big hard lump" you may not have known that. Leave her alone and she'll be fine. It's only when the crop doesn't go down over night and a smell starts to come from their mouth and they can't eat or drink that it's an impacted crop and needs attention.
Just sounds like she pigged out. Let her sleep it off.
It says right in the title "HUGE HARD CROP"
I know a little more than you guys give me credit for..