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 ʻalayhi wa sallam, is His slave and Messenger.
The majority of scholars held that a marriage contract witnessed by a man and a woman only is not valid in the Islamic Sharee'ah. They also held that the absence of the bride's Wali (guardian) or a Muslim judge acting in his stead is invalid unless the woman does not have any eligible Wali to marry her off and there was no Muslim judge in the country. In this case, it is allowable for her to appoint a Muslim man to act as her Wali in the marriage contract and marry her off. For more benefit, please refer to fataawa 83629and 96374.
As for conducting a marriage contract before the woman's ʻIddah expires to other than her ex-husband, it is invalid according to the consensus of all scholars. Please, refer to fatwa 90732.
The ʻIddah of the divorced woman is three complete menstrual cycles if she menstruates, three months if she does not menstruate, or until delivery if she is pregnant.
Allaah knows best.