Frieza's mother is not mentioned in the anime. It could be that Frieza's race (Which doesn't have an official name) are A-Sexuals :). Also we can't know that, because they don't show any females that look at least a bit like Frieza, King Cold or Cooler. So yeah. Frieza might not have a mother. Frieza's mother is mentioned in the Manga. She looks a lot like The Supreme Kai