But they were certainly convinced the translation should be "the virgin" if my source is correct:
SEPTUAGINT (BC 285): Isaiah 7:14 hay parthenos - THE VIRGIN
Actually, St. Jerome did translate “alma” in producing the Vulgate. He was the one who began the Western trend of favoring Hebrew texts over the LXX that the Church had used from the beginning as the Old Covenant Scriptures, which trend in later years the protestants turned into an enthusiasm for recovering the now-unrecoverable ur-text. (I’m not sure he worked with what we now call the Masorete, as the earliest extant manuscript of the Masorete dates to the tenth century A.D.)
I’m even suspicious of the RSV and most more recent translations even in the way they handle the New Testament. The RSV does not follow the Scriptures received by the Church (what Western academic scholars call “the Byzantine Majority Text”), but whatever the translators judge to be the “original” text, and thus mishandles, among other things the account of the healing the man born blind. In the Church’s Scriptures, Christ asks “do you believe in the Son of God?”, in the RSV it’s “do you believe in the Son of Man?” The difference is important, as this is the first sign Christ performed with no parallel among the signs performed by the prophets, and, I think, the only place where Jesus proclaims his divinity to one outside his circle of disciples (other than by addressing the Father as “Father”) Holy Tradition says the man was born without eyes, and that the making of clay was to create eyes for him. Even one discounts this as mere legend, what we now know about the neurophysiology of sight makes the gift of sight to one born blind even with non-functioning eyes at least as much a sign of divinity (hint: it involves instantaneously rewiring the retina and visual cortex which usually take months of seeing in infancy to work properly).