You will unlock cock growing spell only after dedeating Edith.
The Cowgirls are in 1 new ark city near laboratory 2 slums (you need to buy all what she sells 3 times, you find her at devils drink, gentlemens club, main passageway) 3 Transilvania, at graveyard entrance(you need to defeat Edith first)
To enter the graveyard go with rinny to the gate, then talk to the guy nearby. Rinny will then help you fly over the gate if you want.