Taylor Swift's current romance with Calvin Harris might cause Selena Gomez to obsess over ex-boyfriend Justin Bieber. 

A source told HollywoodLife.com that Swift was one of the reasons Gomez was able to stop seeing Bieber. Swift supposedly made sure to remind Gomez to stay busy so that she could move on with her life.  

Now that Swift is reportedly busy dating Harris, she may have less time for her friend. Sources believe it is  likely Gomez will turn to her on-again, off-again lover, being "more vulnerable to falling into some old habits." "The Heart Wants What It Wants" singer's relationship with Zedd could not last, and it has been reported that this is because of her feelings for the Canadian pop star, according to HollywoodLife.com.

After watching Bieber's Comedy Central roast on Skype with the EDM DJ, Gomez reportedly could not stop talking about her former lover to the point where Zedd allegedly felt as though he was the second best following Bieber.

Even when Gomez complained about Bieber, "Zedd could sense that she was still carrying a torch for him."

"She kept asking him if thought Justin had really changed? If it was an act? Just on and on," a source said.

The "I Want You to Know" crooner might go back to the "Boyfriend" hitmaker, as he has been in communications with her. 

Another source claimed Bieber has been flirting with Gomez and is desperate to see her in person, since he is "lonely" and has not been able to find people that "he's emotionally connected to."

"He asks her to come over or suggests they meet up somewhere secretive," the source added.

Meanwhile, the "Come & Get It" singer's breakup with the "Clarity" hitmaker was seemingly amicable, as they decided that they are better off being "just friends," reports HollywoodLife.com.

A source claimed things between Gomez and Zedd were great while they were promoting their single together. However, when they finally returned to their normal lives, they realized "they weren't missing each other" and eventually "drifted apart romantically."