Nicole seems to be out of the Pussycat Dolls, but did she ditch her bandmates, or was she pushed out?

Pussycat Dolls' single Jai Ho was released under the name Pussycat Dolls featuring Nicole Scherzinger and now their upcoming single Hush Hush also has Nicole penned as a solo artist. 

On the dolls' European tour, Nicole sung Hush Hush on her own, while the others were off-stage.

Could it be that Nicole has already left Pussycat Dolls and is staying with them until their Doll Domination promotion and tour is over? 

Is Nicole being singled out as the leader of the group, or is she preparing to go solo?  Is there tension in the doll camp, or are we all just over-reacting to the change? 

So many questions and no answers - sort it out, dolls!