A girl (not woman. Not "young woman", that's a modern concepts), in most of the ancient cultures (I don't talk about modern cultures, that's different), was a woman who were not married.
When a girl was married, she became a woman (it wasn't a matter of age, but a matter of status: being married = to be a woman. Quite different with the nubility.)
And as a non-married woman was supposed to be virgin, both "girl" and "virgin" was perfect synonym (at least in the concept, not always in reality, but it's another thing...)
Of course, it's not true in some societies where the religion didn't prevent to have out of marriage relationship, or where it was not advisable to marry a virgin.
But it's the case in the Hebrew, Greek and Roman societies, for instance.
For the Hebrew society, you can refer yourself to the Old Testament.
For the Greek society, it's mentioned in many texts, for instance, on Wikipedia, they say:
A gamos, a marriage ceremony, was conducted. It started with a sacrifice, proteleia, (premarital), which was for the gods to bless the two being wed. Then the future wife would cut her hair signifying her previous virginity.
For the Roman society, many texts also, for instance:
Celibacy and Fertility
In ancient Rome, all women had to remain celibate before marriage. Their fathers typically arranged their marriage when they were very young, and they were never given the option to date or fall in love. If a man was caught having sex out of wedlock, it was fine, but for a woman, it would be a death sentence. The age of consent was 12 for girls and 14 for boys, but many parents waited for their daughters to have an education before getting married, even if they had been promised to a man for years. They typically got married in their late teens to early 20’s.
Another argument, Minerva was called the "virgo minerva", and it has been described that the meaning was "the chaste Minerva".
So, yes a girl, and a virgin means the same, it's not different from medieval European literature.