Praise be to Allaah.
Ibn Mas'ood (may Allaah be pleased with him) said: "The believer sees his sin as a mountain beneath which he is sitting and which he fears may fall down upon him. The rebellious person sees his sin as a fly which passes in front of his nose and he swats it away…" (Reported by al-Bukhaari, 6308)
This woman's overwhelming sense of the burden of her sin is a sign of faith. We offer her the following advice:
She should make sure that her marriage contract to the second man is also sound, because a marriage between two people guilty of adultery is not valid unless they have repented (see questions # 33); if the contract is found not to be valid, it must be repeated.
If this woman is sincere in her repentance towards Allaah, regrets what she did and is determined never to do it again, Allaah will forgive all her sins, no matter how great they were, so she should not despair of the mercy of Allaah, for no one despairs of Allaah's Mercy, except the people who disbelieve, and who despairs of the mercy of his Lord except those who are astray?
She should hasten to do many good deeds, to expiate for her sin, as Allaah says (interpretation of the meaning): "And perform al-salaat (the prayer) at the two ends of the day and in some hours of the night. Verily, the good deeds remove the evil deeds…" [Hud 11:114]
She should resume a pure Islamic life, based on purity and chastity. Suicide is not a solution at all, as it is one of the most grievous of major sins, and will only increase the punishment of the one who does it. The Prophet SAWS (peace and blessings of Allaah be upon him) said: "Whoever throws himself down from a high mountain and kills himself will be throwing himself down from a mountain in the Fire of Hell for all eternity. Whoever takes poison and kills himself will be taking poison in the Fire of Hell for all eternity. Whoever kills himself with a weapon (literally, iron) will be holding it in his hand and stabbing himself in the stomach in the Fire of Hell for all eternity. (Reported by al-Bukhaari, 5778)
We ask Allaah to help this woman to repent sincerely, to forgive her sins and to include her in His Mercy, for He is the All-hearing Who answers prayers.
Sheikh Muhammed Salih Al-Munajjid