The 'Sorry' hitmaker - who previously dated the brunette beauty on and off from 2010 - was recently filmed hitting out at Selena's new beau The Weeknd, but the 24-year-old pop megastar is said to think Justin is jealous of "what he doesn't have", and has "missed the bus" when it comes to their relationship.
A source said: "Selena is well aware that Justin wants what he doesn't have, but as far as she is concerned, he's missed the bus one too many times."
On Saturday (21.01.17), the 22-year-old singer was filmed slamming The Weeknd's music, as he said he "can't listen" to any of his songs.
Asked at the time if he liked the 'Starboy' hitmaker's music, Justin said: "Hell no I can't listen to a Weeknd song! That s**t's wack."
However, Selena reportedly thinks Justin is just saying that because he's jealous of their budding romance.
The source added to HollywoodLife.com: "She knows Justin doesn't really think The Weeknd's music is whack."
It isn't the first time Justin has reportedly slammed his ex-lover's new relationship either, as it was previously reported he believes the 'Hands To Myself' hitmaker is just using The Weeknd - real name Abel Tesfaye - to boost record sales.
According to reports, Justin thinks the supposed relationship is a strategic move on the part of the Selena - who has previously dated Nick Jonas, Zedd and himself in the weeks before releasing new material - as she is currently working on new material with the 26-year-old musician.
And it isn't just the 'What Do You Mean?' musician who is upset about Selena's relationship with 'The Hills' singer, as the news of their romance caused Abel's ex-girlfriend Bella Hadid to unfollow the brunette beauty on Instagram.