i still wonder why she is #2
In German we have a specific playing card expression "Jungfrau" (= virgin), which is used, when somebody got no trick at all (in trick taking games). In trick taking games this might be very bad (double loss occasionally or other heavy loss), in specific other "negative trick games" like "Ramsch" or "Null" (= zero) in Skat, where the game goal is to get "no points" or "no trick", it's very good, as it doubles the negative point value of the unlucky player, who won most of the points.
"doubling" is naturally connected to the number "2".
"Virgins" (Maids, Junckfrawe) had been in card playing decks long before "Trionfi" became a name for very specific cards (c. 1440), so long before the "Popess in Tarot".
1377 John of Rheinfelden knew 4 maids in a deck with 4x15 structure (with 5 courts).
1455 the Hofämterspiel knew 4 Junckfrawe, but connected them to number "6".
In the JoR deck the Maid was connected to number 12 (which means 10+2), Queens had 14 (10 + 4) and Kings 15 (10+5)
http://a-tarot.eu/p/2013/jor.jpg
... so Arne Jönssen (expert for the JoR text) in "Schweizer Spielkarten 1" (1998) p. 141
So the maid had here a connection to "2" again.
In the common escalation process during a card game in Germany "Contra - Re(contra) - Bock" is said for "doubling", so we get ...
Contra = x2
Re = x4
Bock = x8
.... whereby "Re" associates "Rex" = (king) and "Bock" is an expression, which is also used for a horse (it's slang for a horse, usually used for male sheep or male goat).
Now Rex = King has 4 points in German games usually, Queen has 3 points, and the Jack has two points.
In Tarot trumps ...
the Emperor (trump 4) replaces the king (point value 4)
The Empress (trump 3) replaces the queen (point value 3)
The Popess (trump 2) as the Jack has 2 points
JoR's row had ...
15 king (10 + 5)
14 queen (10 + 4)
13 Ober (upper Marshal, often on horse) (10 + 3)
12 Maid (10 + 2)
11 Unter (lower Marshal, often foot soldier) (10 + 1)
Comparing it with the Tarot row, we have, that the Ober as horseman has disappeared in the row.
15 King - 4 Emperor
14 Queen - 3 Empress
(13 disappeared horseman)
12 Maid - 2 Popess
11 Unter - 1 Magician
In an early Trionfi card version (PMB, and that what descended from it) the horseman reappeared, on the card Justice, which usually has the number 8 (but not in PMB, where we don't know numbers for).
http://a-tarot.eu/p/2013/knight.jpg
... here in a forgery of 19th century
************
So we would have (if Justice was 8) ...
x8 ... Ober = "Bock" = horseman
x4 ... King = "Re" = Emperor
x2 ... Maid = "Contra" = Junckfrawe, Popessa