Portraits come in a wide variety of flavours, one commonly accepted proviso being that the subject is fully aware of why the photographer is there. Even so, some shots, like this one, might be taken in full collaboration with the sitter, while another might be grabbed in an off-guard moment during the same session. In my own mind, directing and collaborating have equal value.
If the subject is absorbed with something, or interacting with another person, the photographer has an opportunity to stalk the character of the sitter. This can be an intimate moment, or the framing can expand to include their relationship to their personal environment. The options seem endless in photography, each image acting as a statement, like a sentence or a couplet in a broader poem.