Well let's take another look, shall we? Here's the bit that you three have homed in on:

"Lady Gaga won a Brit in 2010 for best international female artist, not artiste, chanteuse, or songstress."

The Guardian is quite clearly steering its writers (it's their style guide, don't forget) away from outmoded sexist terms for women performers. It's telling its contributors not to lapse into sexist (chanteuse, songstress) or incorrect (artiste, which has nothing to do with "artist," and if you use that word for a female artist not only are you being sexist but you are also dead wrong). That's the sentiment of that sentence whether you like it or not. There is no hint in that sentence whatsoever that the Guardian thinks that "artiste" means, or has ever meant (it hasn't) "female artist." Two things. Look up the definitions of artist and artiste in a dictionary, and have a good read of the Guardian style guide. It's actually very entertaining and it fully reflects modern thinking on how we must be careful with terminology. Go on, I dare you.