As Chris says - no, because that's the name Pixie picked for herself. Bearing in mind she likely wasn't very old at the time, and she's not super-bright, and there doesn't appear to be any other pixies in existence right now (weird, right?).
Also, the act of picking her name was the first independent act Pixie had committed. Remember that Morgana never bothered to give her a "public" name, apparently because she considered Pixie to be a mistake.
Finally, it would just get confusing if people kept calling Pixie something else when talking to each other and reporting bugs and glitches and requests to me ;P