I pray to Allah to guide your sister and open heart to see the truth and return to the fold of Islam and the straight path.

 

You and your family should turn to Allah in this time of great trial you are facing. Only Allah can open the hearts of people; so pray unceasingly for your sister to come back.

 

You may offer these supplications as often as you wish:

 

Allaahumma ihdi qalbahaa wa ahsin farjahaa

 

Allaahumaa ishrah sadrahaa li al-islam wa zayyinhaa bi zeenathi al-eemaan

 

Allaahumma ruddhaa ilaa deenika raddan jameelan

 

Allaahumaa yaa muqalliba al-quloobi thabbith quloobanaa ala al-haqqi

 

Allaahumma ihdinaa wa ihdi binaa wa ij’alnaa sababan liman ihthada

 

(O Allah, guide her heart to the truth and help her to remain chaste.

 

O Allah, open her heart to recognize the truth of Islam and embellish it with beautify of faith.

 

O Allah, we ask of You to return her gently to the fold of Islam.

 

O Allah, You are the twister and turner of hearts; so, make our hearts steadfast on the truth;

 

O Allah, Guide us to the truth and guide others through us, and make us all instruments of guidance)

 

Having said this, I would also like to point out that you were wrong in insisting that she marries a person she does not like. In Islam, no one including parents has the right to force their children to marry someone they don’t want to. Everyone has the right for himself or herself as long as the person is of compatible faith and character.

 

Almighty Allah knows best.