Look in the area of missing feathers. Do you see a uniform field of emerging pin feathers? That will confirm whether this is molt or not. Feather loss from something other than molt will be bald and smooth.
Molt can sometimes sap the energy reserves of a chicken, so if you have verified molt but you see her start acting lethargic and she is losing weight, you will need to step in with assisted nutrition. I feed canned mackerel once a week to my chickens during molt. Chickens that have poor appetites during molt get fed extra more often until they pep up.