How can a married woman overcome feelings of attraction towards her husband's relative, while trying to build a strong relationship with her husband and adhere to the teachings of her religion?

First, you should thank God for the great blessings He has bestowed upon you, such as protecting you from falling into sin, your husband overcoming unemployment, and having children. All of these are blessings that require gratitude.

Remember that your initial love for your husband was real, so it is not appropriate for you to neglect those feelings. Rather, you should revive them with him at the appropriate time.

No human being is perfect; everyone has flaws. Happy is he who is content with God's decree and thankful for His blessings. Strive to endear yourself to your husband and unite your family, and cut off everything that reminds you of the painful past.

As for steadfastness, there is no greater means than resorting to God through supplication, asking Him to protect you and safeguard your senses from unlawful acts. Seek refuge in God alone.

God Almighty said: (And if an evil suggestion comes to you from Satan, then seek refuge in Allah. Indeed, He is All-Hearing, All-Knowing. Indeed, those who fear Allah – when an impulse from Satan touches them, they remember [Him] and at once they have insight. But their brothers – the devils – they extend them in error, and then they do not stop.) Al-A'raf/200-202.

Al-Sa'di's interpretation of the noble verses clarifies that seeking refuge in God occurs when one feels the whisperings of Satan, and that the righteous, when touched by an impulse from Satan, remember and seek forgiveness, unlike the brothers of the devils who extend them in error.

What you are feeling is most likely a whispering from Satan that will disappear when you occupy yourself with your home, children, and husband, and fill your time with beneficial things.

If the matter has reached the level of attachment, its cure is to cut off hope for this attachment and restrict yourself to what God has made lawful for you.

Ibn Al-Qayyim says: If there is no lawful or destined way for the lover to unite with their beloved, then they must make themselves despair of it. If the illness of love does not cease with despair, then they should remember the beloved's flaws. If all remedies fail, then they should resort to God with sincerity, seeking His aid and supplicating Him.