She sees in her dream that her husband is cheating on her!

If a person is righteous and truthful in his speech, then his
dreams will usually be true, giving him glad tidings or a warning, as
the Prophet (blessings and peace of Allah be upon him) said: “The most
truthful of you in dreams is the most truthful of you in speech.” Narrated
by Muslim (6042). 

However, the righteous may see bad dreams, because there is
no one whose dreams are all true except the Prophets, for their dreams are
revelation. Al-Bukhaari narrated in a mu‘allaq report from ‘Ubayd ibn ‘Umayr
that he said: The dreams of the Prophets are revelation, then he recited the
words (of Ibraaheem to Ismaa‘eel – interpretation of the meaning):
“ ‘I
have seen in a dream that I am slaughtering you (offering you in sacrifice
to Allah)’” [as-Saaffaat
37:102]. 

Al-Muhallab said: In this regard, people are of three levels:

The Prophets, all of whose dreams are true, but some of them
may require interpretation;

The righteous, most of whose dreams are true, but some of
them may not require interpretation;

Others, whose dreams may be true or may be confused, jumbled
dreams. 

End quote from Fath al-Baari (12/362). 

Az-Zarqaani said in Sharh al-Muwatta’ (4/562) 

Some of them said: … The dreams of the righteous are usually
true, but there may occasionally be some confused, jumbled dreams, or dreams
that result from one’s thoughts and ideas that cross the mind.

End quote. 

Hence if the Sahaabah (may Allah be pleased with them) saw a
bad dream, it would upset them and they would fall ill and feel intense
grief because of it, but when the Prophet (blessings and peace of Allah be
upon him) taught them to spit drily to their left, and seek refuge with
Allah from its evil and from the evil of the Shaytaan, and he assured them
that it would not harm them, they were reassured by that and calmed down. 

It was narrated that Abu Salamah said: I used to see dreams
that would make me ill, until I heard Abu Qataadah say: I also used to see
dreams that would make me ill, until I heard the Prophet (blessings and
peace of Allah be upon him) say: “Good dreams are from Allah, so if one of
you sees a dream that he likes, let him not speak of it except to those whom
he loves, and if he sees a dream that he dislikes, let him seek refuge with
Allah from its evil and from the evil of the Shaytaan, let him spit drily to
his left three times, and let him not speak of it to anyone, for it will
never harm him.” Narrated by al-Bukhaari (7044) and Muslim (6040). 

According to a report narrated by Muslim (6037), Abu Salamah
said: I used to see a dream that would weigh heavily on me, like a mountain,
but once I heard this hadith, I no longer cared about such dreams. 

Al-Qurtubi said: What we learn from this is that the one who
sees a dream should not be bothered by what he dislikes in his dream, and he
should ignore it and not pay any attention to it, because it has no basis.
This is the apparent meaning of the hadiths.

End quote from al-Mufhim. 

Once it becomes clear that the Shaytaan plays a role in what
a person sees in his dreams, and that one’s own thoughts also play a role,
then it is not wise and it is not part of Islamic teachings at all for a
Muslim woman to destroy her life and strive to wreck her home because of
what she sees in her dreams. 

Moreover, the Prophet (blessings and peace of Allah be upon
him) recommended concealing the faults of sinners; in fact he even
recommended that the one who sees an adulterer committing adultery should
conceal it and not speak of it to anyone, and he forbade spying, seeking out
faults and disclosing concealed matters in people’s affairs, and it is he
who enjoined caution in that regard, and perhaps one may be certain and have
seen things with one’s own eyes in some cases, but he recommended concealing
it and not disclosing it or spreading it, and not to base anything on it, so
how about if it is the matter of a dream, the reality of which Allah knows
best. 

How many people have seen one particular dream time and time
again, and the same dream was seen repeatedly by other people, then after
that it turned out to be nothing but confused dreams and a case of the
Shaytaan toying with people. 

The Prophet (blessings and peace of Allah be upon him) warned
us about the eagerness of the Shaytaan to cause division among the Muslims
in general, and between spouses in particular. The Shaytaan will never
refrain from using any method to cause division between spouses, either when
they are awake or when they are asleep; rather he will hasten to use it,
because this is one of his foremost priorities. 

It was narrated that Jaabir said: The Messenger of Allah
(blessings and peace of Allah be upon him) said: “Iblees places his throne
over the water, then he sends out his troops, and the one who is closest in
status to him is the one who causes the greatest amount of fitnah
(tribulation or temptation). One of them comes and says, I have done such
and such, and he says: You have not done anything. Then one of them comes
and says: I did not leave him until I separated him and his wife. Then he
draws him close to him and says: How good you are.” Al-A‘mash said: I think
he said: “and he embraces him.”

Narrated by Muslim (2813) 

The woman does not have the right to enquire into her
husband’s past, just as the woman should not tell her husband frankly about
what may have happened in the past that she has repented from. They should
both seek the concealment of Allah. For more information, please see the
answer to question no. 127635.

Conclusion: 

What we advise you to do is to ignore such dreams and not pay
attention to them. Do not try to find out what is concealed of your
husband’s affairs. Be a good wife to him and ask Allah to set things
straight between you and your husband, and to divert from you and from him
all that is bad and shameful, for He is All-Hearing, Ever Responsive. 

And Allah knows best.