She will be lethargic, most likely her eyes will start sinking in, and she will close them. she will stop eating, and drinking. But it's best if you catch it before all this happens, Because once all this takes place the prognoses is usually fairly grim. What you want to do is notice her wanting to lay those eggs so you can make sure she has all she needs to do so. She will look large, restless, hanging around the bottom, slow down, or stop eating, dig holes in her laying ben. When you see this happen give her privacy so not to disturb her.
I would think a mister would be better for a panther, but if your humidity is difficult to maintain then both may be in order. Fogger is used more for the humidity aspects, where as the mister is a way for them to drink, as well as help the humidity. So usually if you are having trouble keeping the humidity up, or like me you have a species that requires more humidity you use both.