A Christian woman
    has the right to ask for a dowry from her Muslim husband
Question

                I am a Christian girl and I want to marry a
      Muslim boy. I am no longer a virgin and he knows about this. Is it right for me to ask for
      dowry from him even I am no longer chaste?
Praise be to Allah.Firstly, we would like to thank you for your question. Secondly, 
  before we discuss the matter of your right to the mahr or dowry, we should discuss 
  the matter of marriage itself. A Muslim man is permitted to marry a chaste woman 
  from the People of the Book (see Question #689 
  and #2527), and she is judged according 
  to her situation at the time of marriage: has she given up her former promiscuous, 
  immoral ways or not? If she is chaste and pure, it is permissible for him to 
  enter into a marriage contract with her, and in this case, the dowry is her 
  undeniable right. In order to resolve the problem once and for all, we advise 
  you to enter Islam, because Islam cancels out all previous sins and wrong deeds, 
  so save yourself from the Fire of Hell and earn happiness in this world and 
  the next. Once you have become Muslim there will be no element of doubt whatsoever 
  concerning the validity of your marriage, and the problem to which you refer 
  in your question will no longer be an issue at all. We ask Allaah to guide you 
  and us, and to give you help and success. Peace be upon those who follow true 
  guidance.