How do lines 4–9 (verum Acerronia ... infertur) give a strong impression of Agrippina's quick thinking and intelligence?

During the shipwreck, Tacitus throws emphasis on Agrippina’s quick thinking and intelligence by juxtaposing the character with her companion, Acerronia. While Acerronia is defined by the qualifying “imprudentia”; Agrippina is “silens”. This is significant because in the context of the shipwreck, Agrippina is quick to realise that keeping quiet is her route to safety. Meanwhile, Tacitus uses the frequentative verb “clamitat”, as Acerronia, pretending to be the emperor’s mother, kept shouting for those around to come to help. This only results in her meeting a grim death at the hands of the assassins.
Agrippina, on the other hand, understands the situation and, despite receiving a wound herself, is all the less recognised, “eoque minus adgnita”, and remains unidentifiable as the target. Her logical escape is then underlined as Tacitus exhibits Agrippina’s balancing actions, “nando…occursu” which enable her escape. Despite the high pressure stakes, the historian suggests that Agrippina remains calm in her pursuit of safety, displaying her quick thinking and intelligence to the highest degree. She is thus conveyed to the safety of the shore, without meeting her death at sea.