Selena Gomez threw a fit over Justin Bieber at Taylor Swift's 25th birthday party at her apartment on Friday, Us Weekly reported.

The former Disney star cried about her ex-boyfriend whom she dated off and on for three years in what many fans called a toxic relationship.

A source told Us Weekly that Selena threw a fit. "She shouted, 'No one understands me! My boyfriend doesn't even understand me," the source said adding that people "just stared [at her]."

The rest of the party had a good time and probably did not see the outburst that happened on the upper terrace of Taylor's Tribeca apartment.

It has not been easy for Selena to see Justin dating 18-year-old Hailey Baldwin, HollywoodLife.com reported.

Her best friend Taylor has been helping her to cope with the situation. After all, the 25-year-old country singer-turned-pop star has had a few bad relationships and has a few great songs to prove it.

"Taylor had been reassuring Selena that she did the right thing by playing hard to get with Justin. She told Selena to stay away from Justin's Twitter and Instagram accounts, to stay positive and to stay busy," a source told HollywoodLife.com.

"When Selena gets in a tough spot and starts obsessing over Justin and what she should have, or could have done, Taylor has her write a gratitude list of the top ten things she's most grateful for."

Hailey has previously stated that she and Justin are just friends. Bieber recently posted a picture of him and the model to Instagram. "People are crazy. I'm super single and this is my good friend u would know otherwise," he captioned.

Justin spent Tuesday playing with Kendall Jenner and Baldwin, according to an Instagram post of the three of them playing Nerf Wars.

Jay Z, Beyoncé, Justin Timberlake, Nick Jonas, Charli XCX and other stars went to the "Shake It Off" singer's birthday bash.

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