"[Demi] is totally upset and disgusted with things," a source revealed. "One of the reasons [Joe] ended stuff with her was because it was getting 'too public', and now he is being very open with his new girlfriend."
According to the insider, Demi was keen to get back together with Joe - but since he got it on with Ashley, Lovato believes "some things were a big lie".
"I think there's a certain level of respect that's lost when that happens," the Sonny With A Chance actress told Hollywood Life.
"But you can't do anything about it other than to just keep going and be glad you have someone in your life that you can think about and spend your time with."