If I had to guess, I'd say it looks like a "Ross's goose" to me, which are not uncommon for your area.
My quick google says eqypians (usually darker colored) are members of shelduck family and females quack/males hiss. There are good youtube videos to hear how they sound.
Whatever she is, if you willing to spend money, get her Mazuri waterfowl food. It is what zoos/aviaries feed exotic waterfowl, and is especially palatable.