The young lovers have been on-and-off for more than two years, most recently breaking up in May when Selena confirmed the split to a Boston radio station saying, "Yep," when asked if she was available.
"Selena's no angel herself, but Justin is certainly not the type of boy she needs," the insider exclusively told Radar.
"She's finally taken some of their advice to heart and swears it's finally over with him, for good. She doesn't see herself getting back together with him and just needs to move on.
The insider says Selena has a lot going on right now to keep her mind off Bieber, and has asked her friends to keep her accountable.
"Meanwhile, Justin is on a downward spiral and Selena wants nothing to do with it. For a minute she thought she could 'save him' which is why they got back together the last time. But she's over him and his childish behavior.
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