Question Summary:
If a women has an affair with her khala’s husband (mother’s sisters husband) does her khala’s nikah become void?

Question Detail:

If a women has an affair with her khala's husband (mother's sisters husband) does her khala's nikah become void?
also can you tell me of some aadiy'a in order to get married soon.

Answer :

In the name of Allah, Most Gracious, Most Merciful
Assalaamu `alaykum waRahmatullahi Wabarakatoh
The root cause for such actions is Muslims not adhering to Shar’ee purdah.  Purdah from ghair-mahram men is compulsory and should be strictly adhered to.  In these times, where evil and sins are predominating, strict purdah should be adopted even between close family members who are non-mahrams.  The husband and the niece have committed haram. Both should seek sincere repentance for their sins.
Nevertheless, the marriage of the aunt is not annulled.  She is still in the marriage of her husband.
Al-Durr al-Mukhtar (3/30) H.M. Saeed Company
Rad al-Muhtar (3/34) H.M. Saeed Company
 
الدر المختار (3/30)
( و ) حرم أيضا بالصهرية ( أصل مزنيته ) أراد بالزنا في الوطء الحرام ( و ) أصل ( ممسوسته بشهوة ) ولو لشعر على الرأس بحائل لا يمنع الحرارة ( وأصل ماسته وناظرة إلى ذكره والمنظور إلى فرجها ) المدور ( الداخل ) ولو نظره من زجاج أو ماء هي فيه ( وفروعهن ) مطلقا  
رد المحتار (3/34)
وفي الخلاصة : وطئ أخت امرأته لا تحرم عليه امرأته...قال ابن عابدين: ( قوله : وفي الخلاصة إلخ ) هذا محترز التقييد بالأصول والفروع وقوله : لا يحرم أي لا تثبت حرمة المصاهرة ، فالمعنى : لا تحرم حرمة مؤبدة
We did not come across any specific dua for getting married soon.  You should make dua after ever salat, as duas which are asked after salat are readily accepted.
عن أبى أمامة قال قيل يا رسول الله أى الدعاء أسمع قال جوف الليل الآخر ودبر الصلوات المكتوبات
Abu Umama (Radhiyallahu Anhu) narrates that someone was asked, “O Rasulullah, which duas are readily accepted?” Rasulullah (Sallalahu Alaihi Wasallam) said, “In the middle of the night and after every fard salat.” (Al-Tirmidhi)
 
And Allah knows best
Wassalam
Ml. Ehzaz Ajmeri,
Student Darul Iftaa
Concurred by:
Ml. Abu Yahya
Student Darul Iftaa
Darul Iftaa, Madrassah In'aamiyyah