I am a young man who is married to a Muslim woman but her family is not Muslim. She became Muslim and learned some soorahs and how to pray via the internet. After we got married I asked her: at whose hand did you become Muslim? She said: I became Muslim by myself. I said to her: You have to utter the Shahaadatayn, so she uttered them before me. Is that correct?
Please note that we got married in the mosque before the Shaykh and a number of witnesses, and she got a certificate proving that she is Muslim.
In order for a person to become Muslim, it is not essential for him to declare his Islam before anyone. Islam is a matter that is between a person and his Lord, may He be blessed and exalted. If he asks people to bear witness to his Islam so that it may be documented among his personal documents, there is nothing wrong with that, but it should be done without making that a condition of his Islam being valid.
No marriage contract is valid without a wali (guardian)for the wife, but no non-Muslim can act as a wali for a Muslim woman. If she has no Muslim wali then the qaadi (judge) or the imam of the mosque or the local mufti (Islamic scholar) may act as her wali.
We ask Allaah to bless you both and to join you together in goodness.