Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Hijab is compulsory (Wajib) for a woman according to many evidences in the Book and the Sunnah. If a Muslim woman does not wear Hijab while she is confessing that it is a Wajib, it is disobedience.
Therefore, we do not advise you to marry this woman as long as she is in that state.
We remind you with the saying of the Prophet (Sallallahu Alaihi wa Sallam): "A woman is married for four things: for her wealth, her family status, her beauty, and her religion. So marry the religious woman; you will prosper."
You should try to make this woman become righteous by asking her Mahrams to whom she would listen to advise her, or by sending her some tapes or booklets. May Allah rectify her condition, and therefore she could be a good wife.