Praise be to Allah.
There is no doubt that asking about the woman’s religious commitment is the first thing that the man should look at if he wants to get married, as the Prophet (blessing and peace of Allah be upon him) taught us. Moreover one of us can rule only on the basis of what appears to be the case, from asking about the woman and her family, and how she is before marriage. So he should not be content with what she shows or what he thinks from her outward appearance or from a few events. If he tries hard to check and ask, then it becomes clear that she is different from what he expected, this is the matter of the divine decree and has nothing to do with him, and in that case he needs to see the best way to deal with the situation.
The matter of religious commitment is a relative matter. When it comes to details, some people want the level of religious commitment that suits them, such as striving hard to offer naafil fasts, pray qiyaam al-layl, memorize the Holy Qur’aan or a specific portion of it, or have some shar‘i knowledge, etc. Others may vary in the level of religious commitment they seek.
In fact, examining this issue and the possibility of getting what you want is to be done before marriage. After marriage, however, there are two possible scenarios:
There is a certain level of religious commitment but it is less than expected or less than required. It is possible to accept this situation, even if it is less than we hoped for, if the level of commitment is limited to doing obligatory duties and staying away from haraam things.
If the woman adheres to that minimum obligatory level of performing duties and avoiding haraam things, then she will be fine, in sha Allah, so long as that includes obedience to her husband.
Imam Ahmad narrated (1573), in a report that was classed as saheeh by al-Albaani, that ‘Abd al-Rahmaan ibn ‘Awf (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “If a woman offers her five (daily) prayers, fasts her month, guards her chastity and obeys her husband, it will be said to her: ‘Enter Paradise from whichever of the gates of Paradise you wish.’”
After that, the man and his wife can work together to do more good deeds and naafil acts of worship.
But the serious problem is if the shortcoming in doing acts of obedience reaches the level of omitting some obligatory duties or falling into haraam actions.
Imam Ahmad (6664) narrated, in a report that was classed as saheeh by al-Albaani, that ‘Abd-Allah ibn ‘Amr (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Every action starts with enthusiasm, then the enthusiasm wanes; anyone whose enthusiasm wanes but (remains within the limits of) my Sunnah will prosper, but anyone whose enthusiasm wanes and drifts away to something else, will be doomed.”
What this means is that there may be times when a person is very energetic and enthusiastic about worship and acts of obedience, then these energetic times are followed by a decrease in enthusiasm, laziness and a drop from the level previously reached. This is something natural and there is the hope that the individual will still prosper, but that is only if, during the times of decreased enthusiasm and weakness, he does not neglect the obligatory duties, because if he abandons them or takes them lightly, he will be doomed.
Doom is not caused by merely falling into sin, for we are all sinners; rather a person is doomed when sins appear in his general behaviour and that becomes his situation most of the time and he does not care or feel regret or repent; rather he persists in that sin and feels at ease with it.
It is clear from the way you described your wife that her decrease in enthusiasm and backtracking is of the type that is dangerous, and indeed is of the type that makes one doubt that she really was as religiously committed as she appeared to be. Even if she has grown lazy about some acts of worship, what does your beard have to do with her that she should feel annoyed by it?!
What you have to do now is not to show any compromise towards her situation. Being too lazy to get up for Fajr prayer is a major sin and serious offence. In fact it is kufr that puts one beyond the pale of Islam according to many of the Companions of the Prophet (blessings and peace of Allah be upon him). That was also stated in a fatwa by Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah have mercy on him). So it is not permissible for you to approve of that. If ghusl is what is preventing her from getting up, then you should not let her go to sleep except in a state of purity, so that she will have no excuse.
We share your anxiety about your wife and we advise you to delay having children with her and to try again with her. If you see that she is praying regularly on time and is serious about it, including – first and foremost – Fajr prayer, and she is obeying you and fulfilling the rights that you have over her, then be patient with her for a while and see how things go. Try to discipline her and teach her, and be patient in putting up with her crookedness and weakness, in the hope that Allah may guide her and set her straight.
But if you find that she is persisting in neglecting the prayer or trying to interfere with your religious commitment and objecting to your beard, then there is nothing good for you in her and we advise you to leave her before having children from her, which would only make the problem more complicated.
We ask Allah to guide you.
And Allah knows best.