If a woman wants to marry any man she should have 2 conditions:
1-not to be already married
2-promise not to commit infidelity after marriage
but just being a maiden and saying that one will be faithful, doesn't mean that she can marry anyone. suppose an ordinary girl (a homely swineherd for example) living at the time of St.Louis the monarch, comes to him and says :"your Majesty, I am not married and I will be faithful to you, then accept me as your wife" It will be ridiculous and everybody will say that it is persumptous for her to covet such a title.
Now, the Holy Church, calls some women, brides of Christ(in a literar sense not metaphorically), and what have thses women done to desreve to be called so?: the above mentioned 2 conditions:
1-not being married already(being virgins or widows)
2-promising to remain faithful (vowing not to take any other spouse than Jesus=Vow of chastity
then by mere fact of fulfilling these conditions they become greater than any earthly empress or queen, since Jesus is greater than any king or emperor.
But it sounds too cheap to me...... such a great title, just because you vow to never marry????????