、。
Although she had no prior knowledge of the subject, she always grasped it neatly.
Literal
She [topic-は] that matter [concerning-に関して] any background-knowledge [also-も] not-existed [despite-のに], always neatly understood.
This sentence stacks several flavors of grammar. に関して ('concerning, regarding') is a slightly formal alternative to について; 何の~も~ない ('no X at all') is the emphatic negation pattern using 何の as a determiner ('any kind of'); のに carries 'despite, even though', tying the lacking-knowledge clause into concession against the always-understanding outcome. 予備知識 — literally 'preparatory knowledge' — is the standard term for background or prior knowledge expected before an activity. きちんと is a 擬態語 mimetic for orderliness, neatness, properness; applied to understanding it suggests grasping things cleanly and completely rather than vaguely.