Edit: now the posts don't get deleted so the discussion seems to be alright?
Then to clear this up, after taking a look at the japanese text and wikipedia, it is clearly a general statement. There is at least no "only
one little girl" or "only
that little girl" in the original text and while theoretically it can mean "only little girl/s", it isn't explicit at all and you'd normally understand it as "only little girls in general" . And then wikipedia also states "girls" in general.
What do you think is the reason behind that behavior? If I recall correctly Priscilla herself was a little child when her family got killed, therefore maybe inconsciously she won't kill other little girls. If she's really evil she maybe wants them to feel the same pain as she did? But there should be quite a few other Claymores wanting to seek revenge on Priscilla ^^;