Her husband engaged in foreplay with her in Ramadan, and she thought to let him have intercourse with her so that he would break his fast and be sinning! Did she break her fast with this intention?

Praise be to Allah.

Firstly: 

If a person intends to break his fast whilst he is fasting, and has decided to do so, and is not hesitant about it, his fast is rendered invalid according to the correct opinion, even if he changes his mind about that intention, and he has to make up that day. 

But if he is hesitant about breaking the fast, or makes it conditional upon something, such as if he says: If I find food or drink, I will break my fast, then he does not find anything, in that case his fast is still valid. 

Ash-Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was asked:

A man was travelling and fasting in Ramadan, and he intended to break his fast, but he could not find anything with which to break his fast. Then he changed his mind about that intention and completed the fast until Maghrib. Is his fast valid? 

He replied:

His fast is not valid and he has to make it up, because when he intended to break the fast, he broke the fast. But if he had said: If I find water, I will drink it, otherwise I will continue my fast, and he did not find water, in this case his fast is still valid, because he did not definitely intend to break it; rather he made breaking the fast conditional upon the availability of something, and that thing did not become available, so his original intention remained in effect. 

End quote from Liqa al-Bab al-Maftooh (29/20). 

What appears to be the case is that what happened with you is the latter: in other words, you made breaking the fast conditional upon your husband continuing with this matter, which he did not do. Intending to break the fast is one thing, and making it conditional upon something that did not happen is something else, on which the ruling is different. 

Based on that, your fast is valid and you do not have to make it up.

But if you did intend to break the fast, or you think it most likely now that this was your intention, then your fast was invalidated and you have to make up that day. 

If you feel something like that in your heart and you want to be on the safe side and fast another day to make up for that day, then this is good, in sha Allah. 

Please see the answer to question no. 95766. 

But if you are usually affected by waswas regarding your intention or the validity of acts of worship, then do not repeat the fast of that day, and assume that it was valid. Beware of getting carried away with waswas, for this leads to much trouble and evil, and will not stop until it spoils a person’s worship and his religious commitment as a whole. 

There have been many answers on our website that warn against getting carried away with waswas. 

Secondly: 

If a man is able to control himself and prevent himself from getting carried away and transgressing the limits of Allah by having intercourse or ejaculating, then it is permissible for him whilst fasting to engage in intimacy with his wife by embracing her, kissing her and so on. 

Please see the answer to question no. 49614. 

Thirdly: 

It is not permissible for a woman to try to make her husband fall into a haram action, or to approve of that. Rather what she must do is stop him and prevent him from doing that to the best of her ability. The Prophet (blessings and peace of Allah be upon him) said: “Whoever among you sees an evil action, then let him change it with his hand [by taking action]; if he cannot, then with his tongue [by speaking out]; and if he cannot, then with his heart – and that is the weakest of faith.” Narrated by Muslim (49). 

Letting your husband do that, without trying to stop him, so that he would do something forbidden, commit sin and be exposed to the punishment of Allah in the month of mercy is a haram aim and striving to make someone commit an act of disobedience to Allah, or approving thereof. Ash-Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said: 

The one who sees someone eating or drinking in Ramadan, and knows that he is fasting, should remind him, because if he forgot then he is excused, but you did not forget. Allah, may He be exalted, says (interpretation of the meaning): “Help you one another in Al‑Birr and At‑Taqwa (virtue, righteousness and piety)” [al-Maidah 5:2]. 

Al-Liqa ash-Shahri (70/44) 

If this is obligatory with regard to all people, then how about if it is one’s husband? Undoubtedly in this case it is even more obligatory, and his rights over you are more emphasized. 

So you must repent and seek forgiveness, and not do such a thing again. You should be the best helper to your husband in matters pertaining both to this world and the Hereafter, therefore, if you see him committing a sin or wanting to commit a sin, you should tell him not to do that and remind him of Allah. 

And Allah knows best.