Is it permissible for a Muslim woman to marry, after she had promised God not to marry if He forgave her sins, given that she was Catholic and committed sins, then repented?

No one has the right to stand between you and sincere repentance, for Allah is All-Forgiving, All-Merciful, and He accepts the repentance of His servants, as stated in His glorious words: (Say, "O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the All-Forgiving, the All-Merciful"), and in the Hadith (definition) Qudsi: (O son of Adam, so long as you call upon Me and hope in Me, I forgive you for what you have done, and I do not mind). You must turn to Allah with good expectations and forget the past, for "Islam demolishes what came before it." As for devoting oneself to worship and forsaking marriage as a means of drawing closer to Allah, this is not part of the Islamic Sharia (definition); rather, it contravenes the Sunnah (definition) of the Prophet (peace be upon him) who said: (Whoever turns away from my Sunnah is not of me). Any vow or pledge to abstain from marriage is invalid and without legal effect, and it is not obligatory to fulfill it; instead, an expiation for breaking an oath is due.