All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
The view that we hold the most valid is that the consent of the bride's Wali (guardian) is a condition for the validity of the marriage contract; and this is the opinion of the majority of scholars, contrary to Abu Haneefah who is of the view that the marriage contract is valid without a guardian. Please refer to Fatwa 83629 about the conditions of a valid marriage contract.
Therefore, according to the view we adopt here in Islamweb, your marriage contract must be invalidated and you may renew it with the consent of the guardian in case you wish to continue the marriage bond. For more benefit, please refer to Fatwa 131952
However, if a Muslim judge ruled that such a marriage is valid, or if the marriage contract was conducted on the basis of following the view of Abu Haneefah, then the marriage is effective and it is not an obligation to renew it in this case. For more benefit, kindly refer to Fataawa 89782 and 130284.
As regards how to validate this marriage contract, you have the choice either to propose personally to her guardian or for your father or anyone else to do so, or for the girl to inform her father of your wish to marry her.
As regards informing her guardian about the previous invalid marriage, or not informing him about it, you should take into consideration what you know about his character and you decide accordingly which option you deem appropriate.
If it was presumed that her guardian would refuse to give his daughter in marriage to you while she is willing to marry you, then she may take her case to an Islamic court, and if it is proven for the judge that her guardian is refusing to marry her off without a sound reason, then the judge will marry her off to you or he will appoint someone to do so, or he may ratify her previous marriage if he believes that it was valid.
Allaah Knows best.