A women that I know, I told her that I can't marry a non-Muslim woman until she accepts Islam. She has read a bit of the Quran and about Islam, but was not convinced about Islam or if Allah the one real God. Surely, nobody can change what she believes in her heart. But for her, is it okay to say the shahada and start to pray? Is she then Muslim? Can I then marry her?
A women that I know, I told her that I can't marry a non-Muslim woman until she accepts Islam.
First, I want to point out that this is not entirely accurate. Muslim men are permitted to marry chaste women of the Book (typically Christians and Jews).
... And [lawful in marriage are] chaste women from among the believers and chaste women from among those who were given the Scripture before you, when you have given them their due compensation, desiring chastity, not unlawful sexual intercourse or taking [secret] lovers. ...
The shahada is in the Qur'an:
- لَا إِلَٰهَ إِلَّا اللَّهُ ("There is no deity but Allah") is in Qur'an 37:35 and
- مُّحَمَّدٌ رَّسُولُ اللَّهِ ("Muhammad is the Messenger of Allah") is in Qur'an 48:29.
Disbelief in the contents of the shahada is disbelief of Islam.
If she says the shahada and doesn't contradict it nor major aspects of Islam (kufr), then from any Muslim's point of view she's a Muslim, and therefore legally marriageable. However, there might be some technical hurdles to jump through to organize a marriage (e.g., an imam might request a certificate of conversion).
There are ahadith which indicate even the Prophet Muhammad was unwilling to contradict someone who says the testimony of faith (Sahih al-Bukhari 6872 and Sahih al-Bukhari 6865, 6866). Allah can reliably determine who has phony beliefs; humans cannot.
This is exemplified through the stories of Prophet Nuh and Prophet Lut's wives:
Allah presents an example of those who disbelieved: the wife of Noah and the wife of Lot. They were under two of Our righteous servants but betrayed them, so those prophets did not avail them from Allah at all, and it was said, "Enter the Fire with those who enter."
That being said, ahadith indicate that it's best to marry a pious woman:
A woman is married for four things, i.e., her wealth, her family status, her beauty and her religion. So you should marry the religious woman (otherwise) you will be a losers.
Sahih al-Bukhari 5090
It's likely in nobody's best interest to marry someone who is borderline Muslim.
Yes she can.
When a non muslim makes a shahda, they must be treated as a muslim and considered a muslim. You can never be 100% sure if this person belives or not. These are matters of the heart. Secondly, if a person is converting for marriage means they are willing to adopt something different from what they had before.
The prophet ﷺ used to know all the hyporcites and yet treated hem like muslims. During war, if the enemy says the shahda in fear that they will be killed, they used to be instantly treated like muslims. These is proof that saying the shahda is sufficiant to be considered a muslim. This is also permissible for marriages.
It is important to distinguish that they might not be sincere today, but being in the fold if islam, they will have a chance at being a practicing muslim. Marriage has its wisdom and as the man, this person is expecting to act like a muslim and this comes slowly and gradually.
You can marry anyone who says the words and means it.
1. So imagine right now in your mosque there are 1000 Muslim women. You can marry each and every one of them, because there's nothing to suggest that they said Shahada while not believing it. Even if another person tells you they don't mean it, still until you're not 100% sure you can still marry them.
2. However if you know a person who has said Shahada but has never meant it and just saying for deceiving then it's no different than not saying it. <-- You must know this for sure.
3. Having that said what you're asking is slightly different. She has said but still isn't sure, she likes Islam but not all the way. My point is this person isn't in denial, nor in the phase of acceptance which makes me uncertain...it really depends on your school of thought.
If it's option1, you can marry, if it's option2, you can't marry, if it's option3 you should ask your scholar or give us more information about your school of thought, but it should be pretty straightforward.