It was way more important for them at this time then it is for most of women in our occidental and modern society.
From historical sources I know, I agree with Torpedo here, it was mostly facade as it is today in less developed countries where they care about such stuff as people did in middle ages in Europe. One of main reasons why it is facade is that virginity cannot be verified.
If I remember correctly roughly 50% (or maybe 30% something around that number) of women will never get their hymen damaged by sex as theirs is too flexible and even if is gets damaged it is really hard to spot scarring as hymens come in lot of shapes and sizes so it is hard to know if it was there from beginning or if it is scar.
And lastly hymen can be broken in various non-sexual ways like riding a horse, running, swimming.....
So in middle ages it worked like this, you kept your reputation roughly ok and when verification time came you bribed whoever was checking that virginity.
Also people didnt cared much about virginities of queens and princesses as they were mainly means to the end.....hell they would marry horse if it would give them same amount of stuff.....or sister if it would keep their stuff in their pocket...Habsburgs...ehmm ehmm...
Btw just to add small vote to the pile, I am also interested in pregnancy and would be happy if it would be added, something like generic short progression pregnancy system with room for children with not much influence on the plot.......or maybe use them as tools of diplomacy, similar to Queen Victoria aka "grandmother of Europe".
Of course it is just suggestion, final decision is yours dev.