What is the ruling on someone who causes trouble between an engaged couple so that he will call it off and she can snag him?

Question

Praise be to Allah.

Firstly:

Causing trouble between Muslims is a major sin that corrupts intentions in
people’s hearts, spoils relationships between people, and spreads mischief
in the land.

It
says in al-Mawsoo‘ah al-Fiqhiyyah (5/291):

It
is prohibited to cause trouble and spoil relationships among Muslims, for
two reasons:

1.in order to
preserve unity among the Muslims

2.out of respect for
their dignity, because Allah, may He be exalted, says (interpretation of the
meaning): “And
hold fast, all of you together, to the Rope of Allah (i.e. this Qur’an), and
be not divided among yourselves”
[Aal ‘Imraan 3:103].

Hence reconciling between people is one of the best of good deeds, and
causing division among people is one of the gravest of major sins, as the
Prophet (blessings and peace of Allah be upon him) said: “Shall I not tell
you of something that is better than fasting, prayer and giving charity? ”
They said: Yes indeed. He said: “Reconciling between people, for causing
division among people is the ‘shaver’ (that shaves one of religious
commitment).”

Narrated by at-Tirmidhi (2509); classed as saheeh by al-Albaani in Saheeh
al-Jaami‘ (2595).

Hence the Messenger (blessings and peace of Allah be upon him) forbade
seeking out the faults of the Muslims, and he forbade backbiting, malicious
gossip, suspicion, mutual hatred, mutual envy and everything that may lead
to causing trouble among Muslims. End quote.

This prohibition is emphasised if causing trouble between people is done to
spoil that which could have been the means of bringing them together,
instilling love between them and uniting them, such as marriage.

Secondly:

Causing trouble between people usually involves telling lies, backbiting,
malicious gossip and slander, all of which are major sins. Please see the
answers to questions no. 23328,
101776 and 99554 for information on the negative
impact of these blameworthy characteristics and how to repent from them.

Thirdly:

It
is haraam for a Muslim woman to cause trouble between a man and his fiancée
so that she may snag him for herself, for this comes under the heading of
bad conduct and blameworthy characteristics. Al-Bukhaari (6601) and Muslim
(1408) narrated that Abu Hurayrah (may Allah be pleased with him) said: The
Prophet (blessings and peace of Allah be upon him) said: “A man should not
propose marriage to a woman to whom his brother has already proposed and he
should not outbid his brother. A man should not marry a woman if he is
already married to her paternal aunt or maternal aunt. A woman should not
ask for her sister to be divorced so as to deprive her of what is rightfully
hers and so that she may be married in her stead; rather she will have what
Allah has decreed for her.”

An-Nawawi (may Allah have mercy on him) said:

What this hadith means is that it is prohibited for a non-mahram woman to
ask a man to divorce his wife and marry her instead, so that she gains the
maintenance, kind treatment, intimacy and so on that belonged to the
divorced woman.

End quote from Sharh Saheeh Muslim (9/193)

Al-Haafiz (may Allah have mercy on him) said:

This is quoted as evidence for the prohibition on a woman proposing to a man
who has already proposed to another woman. This hadith makes the ruling
concerning men the same as the ruling concerning women with regard to
proposing marriage. The scenario is: a woman proposes to a man, and he
responds to that proposal, then another woman comes and encourages him to
marry her, and tries to make him lose interest in the one who came before
her, whom he has already agreed to marry.

End quote from Fath al-Baari (9/200)

Fourthly:

The issue does not have to do with whether all the parties involved in this
issue know what is happening or not, because worldly matters may be hidden.
But on the Day when all secrets will be exposed before the Lord of the
Worlds, and what was hidden in people’s hearts becomes manifest, what answer
will those who caused trouble and spread malicious gossip have before
Allah?

What the woman who has done this must do is hasten to repent, and part of
complete repentance is putting right that which she has spoiled and
admitting to each party what she said about the other, so that they will
understand the situation, then if they want to they can get back together
and go ahead with their marriage, or if they want to they can remain as they
are now.

If
it is too difficult to state what really happened, then that can be done by
way of hinting or via a third party, striving to set things straight and
explain what really happened.

Please see also the answers to questions no. 14092
and 178714

And Allah knows best.