|Dark green 'River Cabbage' has the essential amino acids|
While he was basically starving, the woman went out and found food... food that didn't run away and didn't fight back. In this image, she is offering him 'River Cabbage'. I'm not exactly sure of the actual species as I'm not up on my South American wild edible plants. However, a dark green broad leaf like that would certainly be packed with nutrients, such as Vitamins A, C, K, B (specifically Folic Acid), and minerals like potassium and calcium. The calcium can have less bio-availability in some dark green leaves due to oxalates. This slight problem is solved by heat.
Many dark green leafy plants contain all of the essential amino acids: tryptophan, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, valine and tend to have some of the non-essential amino acids as well.
The human body stores amino acids. You do NOT have to have a complete protein in every meal in order to get the protein you need.
Plus, she found fruits, edible flowers, and other plants, so even if River Cabbage is slightly low in one of the essential amino acids, there is a good chance that should would have gotten it elsewhere.
As expected, his energy petered out and though she felt a bit weak, she had no energy issues like he had.
I do get thoroughly tired of every survival show preaching about protein. It's really NOT that difficult to get what you need and 21 days is not long enough to do permanent bodily damage if you didn't get any... period.