That is not normal AT ALL! High Production layer hens get large combs, but not like that. The comb will always be hot to some extent as the bird uses it to cool itself off by pumping hot blood to the comb which causes heat to be released to the atmosphere. Compare the temp of her comb to another bird. If she is noticeably hotter, than something is wrong. Also, a swollen comb like that is symptomatic of a few serious respiratory diseases (can't remember which off the top of my head, but I think Laryngo, Coryza, and IB cause swelling like that). Is she have any trouble breathing? Nasal discharge, watery eyes, wheezing, coughing, gagging, etc? I'd isolate her immediately. You could have potentially introduced a serious disease into your flock.