Finally the need for the young women to get married was addressed. That being said, the women seeking marriage partners would be kind of passive, that is, they'd merely attract the attention and fancy of a man. The man would then need to approach the parents (or the guardian) of the maiden, hoping the parents weren't already arranging a marriage for their daughter elsewhere. If they were, the man would need to hope he can offer a better deal (a better future for the young woman, if the parents were decent and not only looking for their own benefit). Possibly the man would need to check it with his own parents as well, especially if he's still young himself. Typically the man would be a bit older to have a secure income to provide for the family. Of course if it's a son from a rich family, the ability to provide would be of no concern, but his parents would be more interested in the background of the girl and thus have their own preferences and ideas.
I suppose there might have been certain demand for spinsters as a workforce, but I reckon it wasn't huge. Nuns ran their own facilities in a natural way, anyway. A widow might have seemed less pitiful or suspicious as well (since people would always wonder what's wrong with a woman if she couldn't get a man). The past wasn't a jolly place.