In George bernard Shaw's book, Saint Joan, who can tell me about the marriage proposal?
I think you have become somewhat confused with maybe another text. First of all, this is a play by the famous playwright, George Bernard Shaw, and secondly, it contains no marriage at all. The central female character, Joan of Arc, is a young woman who believes she has been chosen by God to redeem France from the English, and who manages to persuade the Dauphin, the Prince of France, that she will see him crowned King of France in Rheims. She is a virgin and never becomes involved with men romantically. As a result, there is no marriage proposal in this excellent play.
I have included some links below to direct you to the enotes study guide section of this play to help you consolidate your knowledge about this important text. I hope this helps!
I can't really remember there is a marriage proposal but I can recall that some of the characters were moved at first by Joan character, particularly the Archbishop of Rheims but later was disgusted by her pride and her obstinate behavior as she could have been the threat to the church's foundation.