I keep seeing everyone refering to Van Hydrus as a 'he'; I can't be the only one absolutely certain it's a she under that helmet, can I?

I had a feeling just based on her interaction with the Emperor when we first see them; she gave me a bit of a Livia feel, and something about her body/armor shape strikes me as feminine, despite the blessed lack of boob plate, but I was stumped as to how to prove my theory...

Well, Garlean names follow a Latinesque naming convention, and based on Latin grammatical rules, 'Regula' is clearly a female name; a male would be named Regulo or Regulus. Granted, we only have two other named Garlean females, but both of them have names ending in 'A', which on a Latin noun indicates that the subject is female.