At first I was going to leave her without a name, but I finally decided to go for it because I wanted to inject a little bit of personality to the character, and also I wanted to able to address her without calling her "Female anon" all the time.

I played around with a few options and I finally settled with "Onna" for a few reasons.

If you haven't noticed, the name "Onna" is just Anagram for "Anon" that by coincidence shares a phonetic connection with the term used in Japanese For "Female" (女 "on'na"), but people who speak Japanese and also some anime fans out there probably already noticed that.

However, according to my research, the word "Onna" by itself is not a formal way of referring to a girl in japanese, so If you ever need to address a woman in that language use any of these instead: 
  • 女の人 (onna no hito) 
  • 少女 (shoujo; “girl” ) 
  • 女の子 (onna no ko; “young lady”) 
  • 女性 (josei; “woman”) 

I figured I need to be clear about it to not spread misinformation on that subject.

I just thought that the connection was too good to let it slide, but I'm explaining it just so everyone knows there's no mischievous intentions behind it.