Justin Bieber deleted his Instagram account overnight after sparring with ex Selena Gomez
Credit: Larry Marano/Getty; Rachel Murray/Getty

Selena Gomez‘s drama-causing Instagram comment on ex-boyfriend Justin Bieber‘s page may have stemmed from residual feelings the star still has for the singer, a friend of Gomez’s tells PEOPLE exclusively.

“He was Selena’s first love, and she hasn’t been able to totally get over him,” the source says.

The revelation comes shortly after Gomez seemingly apologized for issuing her take on Bieber’s threats to leave social media – warnings he followed through on early Tuesday by deleting his Instagram.

“What I said was selfish and pointless,” Gomez, 24, wrote on Snapchat, also Tuesday.

Gomez and Bieber, 22, dated on-and-off for several years until late 2012. The “Sorry” singer is now dating 17-year-old Sofia Richie, who is at the heart of the former duo’s current spat.

Bieber threatened to make his Instagram private if his fans continued to write negative comments about Richie. In response, Gomez wrote on the photo posted by Bieber, “If you can’t handle the hate, then stop posting pictures of your girlfriend lol – It should be special between you two only.”

She continued, “Don’t be mad at your fans. They love you and supported you before any one ever did.”

In response, Bieber wrote, “It’s funny to see people that used me for attention and still try to point the finger this way. Sad. All love.”

For more on Justin Bieber and Sofia Richie’s new relationship, and all the details on drama with his exes, pick up the latest issue of PEOPLE, on newsstands Friday.

A source close to the “Revival” singer told PEOPLE, though, that Bieber’s accusation is far from true.

“They’re both young and have made mistakes, but she has never used him,” the insider said. “He put their relationship out there way more than she ever did, and he’s been very strategic about it. Whenever something good is happening in her life, he’ll post something to get at her.”

The singer has previously shared a number “throwback” photos with Gomez to Instagram, despite having no plans to reconcile.