“Her name is Lam Thi Dep (Dep means beautiful in Vietnamese), the picture was taken in 1972 at Soc Trang Province by Vietnamese journalist Minh Truong. “You could find women like her almost everywhere during the war”, said the photographer. “She was only 24 years old but had been widowed twice. Both her husbands were soldiers”. She’s wielding a M-16, the standard issue American soldier’s rifle. Usually this type of photos were taken for propaganda purposes. North Vietnamese women were deeply involved at all levels of the military campaign throughout the war, especially at the business end, fighting against the American-led forces in the jungle.” https://rarehistoricalphotos.com/female-viet-cong-guerrila-1972/

With some images like this one the authenticity is unclear. It does look like a propaganda photo but there is not enough evidence to state that with “confidence.” The photo is still important though and knowledge can be gained by studying it.