Is it permissible for a widow to marry secretly without the knowledge of her family or guardian?

For a valid marriage (Nikah), there are conditions, including the guardian (wali) and witnesses. If a woman is married without the permission of her guardian, the marriage is invalid. The existence of children is not a legal impediment to marriage. If the guardian refuses to marry the woman to a suitable suitor, she has the right to refer the matter to the Sharia judge to arrange her marriage, because the guardian has no right to prevent his ward from marrying someone she approves of, who is suitable. Shyness that prevents one from demanding the right to marry is blameworthy. Caution must be exercised to avoid falling into temptation with a man if a legal marriage is not readily available.