Nikaah & Marriage Issues

Wife making dua that her husband divorces his second wife

Q: If one's husband has made nikaah without telling her and she found out about 3 months later. Her husband did not consummate the marriage and after consulting with his seniors, he regrets what he had done. However he is afraid to divorce the second wife due to backlash. The first wife wants to make dua that he leaves his second wife since he hasn't caused her to to become pregnant which will further complicate things. 

My question is, is one allowed to make a dua as such... "Oh my beloved Allah you create a good excuse for my husband to leave his second nikaah with aafiyah and you make it such that she finds a better spouse for her thereafter". 

Will this kind of dua be allowed?

Nikaah without witnesses

Q: If a boy texts message a girl saying, "Do you accept me in nikkah" and the girl texts back,"yes" and then the boy texts, "same here", and during this there is no witness on the girl's side but the girl does not know if there were witnesses on the boy's side or not. Is the nikaah valid?