Praise be to Allaah.
You should treat your mother respectfully, and try to persuade her to
agree to your marrying this girl who has repented and is practising her religion. But if
your mother does not agree, and you cannot be patient and you fear that you will fall into
sin if you do not marry her, then it is still permissible for you to marry her. And Allaah
is the source of strength.