波西杰克逊的一些疑问

在第五部里，有提到 Blackjack 是三年前从Princess Andromeda逃出来的。可是在第二部里，唯一有提到的飞马是:'Before he could say anything, Agrius, the bear-man, burst onto the deck leading a flying horse. It was the first pure-black pegasus I'd ever seen, with wings like a giant raven. The pegasus mare bucked and whinnied. I could understand her thoughts. She was calling Agrius and Luke some names so bad Chiron would've washed her muzzle out with saddle soap.'
是波西镐错马的性别，还是作者的失误。
还有，在第一部里，Grover 有说过一句：’You're probably a child of Hermes. Or maybe even one of the minor gods, like Nemesis, the god of revenge.'
Nemesis 不是女神吗？