"Cheap Thrills" was written by Sia and Greg Kurstin, and produced by Kurstin. It was originally intended to be performed by Rihanna for her album Anti, but was rejected by her and Icona Pop.
Demi is salty over the fact that she is a complete loser at everything. Even Selena, whose album sales are embarrassingly bad (but still double Demi's), has smash hits.
Taylor hasn't responded to anyone since last summer. Demi is just trying to drum up attention.
Demi's probably just trying to get some publicity since her co-headlining tour with Nick, which had to be saved by Honda in order to even happen, is flopping hard