Is an 'Urfi marriage considered valid if it was not publicly declared with witnesses and consummation did not take place, despite there being private encounters between the spouses?

Marriage without a wali (guardian) is invalid according to the three Imams and must be annulled. Its validity is only recognized if the contracting party is following the Hanafi school based on a reliable preference, or if a ruling validating the contract is issued by a Shar'i judge. Being in a foreign country does not prevent you from obtaining the permission of the woman's wali; he can appoint a representative or even appoint you to complete the contract. As for the witnesses, if the intent behind their distance in acquaintance and kinship is not detrimental, and apparent uprightness suffices for them, then there is no harm. However, a marriage is fundamentally invalid without witnesses. So, if the contract was made without witnesses, it is invalid. Concealing the contract or not publicizing it does not invalidate it as long as the other conditions are met. If the contract is valid, she is your wife; otherwise, she is a stranger to you, and the marriage must be annulled.