How does the author use foreshadowing in Disorder and Early Sorrow?

Ingrid is a markedly deceptive character whose entire life appears to have been comprised of sham and impersonation. She is said to know how to "wind masters, and even headmasters, round her finger," and she is in school working for a certificate that she never plans to use. The performance that she
and Bert put on in the bus, at the expense of the unhappy old gentleman sitting opposite them, in addition to the delight she takes in ridiculing Max Hergesell's nasal drawl reflect a bizarre and sadistic inner quality. Both she and Bert foreshadow through their outward behavior the pose and affectation which will later distinguish the many painted figures who turn up for the party.