Balyn wasn't a roundtable knight as far as I know.

EDIT: Misread your post. Right, Balin's still for Arthur's court even if he's not a member of the Round Table.

Though, there's still Gareth that was a female as confirmed by Garden of Avalon and Camelot stuffs in Nasu's blog.

So it's weird unless Nasu decided to retcon something or Gareth was hiding herself in the same way as Saber. I don't think we have any images of her anyway.

[@Rin]