Queen Ingrith is an ogress, like in the original fairy tale
Which gives another explanation as to why she hates fairies. Her mentioned brother and father could be ogres too. Heck, maybe her home kingdom was one entirely ruled by ogres. Maleficent and Ingrith will form an Enemy Mine pact.
Perhaps one of the other dark fairies turns out to be the Big Bad and will endanger Aurora and/or Phillip, prompting both women to bury the hatchet and save their loved ones. The "Mistress of Evil" actually refers to Ingrith.
