Have you studied Latin? Oh, good.
The line, "O clemens, o pia, o dulcis Virgo María" is commonly translated, "O clement, O loving, O sweet virgin Mary."
I haven't studied Latin, but I was messing around with a dictionary, and it seemed to me that this could be translated, "Gentle, pious, kind Virgin Mary."
What do you think?
Have you studied Latin? Oh, good.
Yes, 4 years of formal instruction, and an additional 8 years of keeping up on it regularly.
Clemens - kind, gentle, or...clement
Pia - pious, prayerful
Dulcis - sweet (both in the sense of taste and in the sense of personality)
So, I think the standard translation is very good.