Is it permissible to marry secretly without the guardian's knowledge, in order to avoid falling into temptation?

The presence of a non-observing (mutabarrija) paternal cousin in the house and being alone with her (khalwa) is forbidden (haram). The obligation is to remove her from the house to another dwelling, or to marry her lawfully with the consent of her guardian (wali). As for secretly marrying her without the knowledge of her guardian and without witnesses, it is null and void (batil wa fasid); because the guardian, witnesses, or public announcement are conditions for the validity of the marriage (nikah).