Selena Gomez instructed Justin Bieber "to lose the constant string of girls" if he wants to have any chance of reconciling their on-again, off-again relationship.

According to HollywoodLife.com, the 21-year-old "Baby" crooner will have to play by all Gomez's rules if he has any hope of winning back her affections.

Since he and Gomez last split sometime last year, Bieber has been romantically linked to a number of females, most recently Kendell Jenner and Hailey Baldwin. In fact, HollywoodLife reports the three are now rumored to have made a wager over the upcoming Mayweather vs. Pacquiao that could end up in the three engaging in a threesome.

The mere thought of that can't sit well with the 22-year-old Gomez, who is also rumored to be pressuring Bieber about his budding friendships with both Mayweather and R&B star Chris Brown.

"Selena hates that Justin is friends with Chris Brown and Floyd Mayweather," a source told the website of the two men who have been convicted of charges related to abusing women. "As much as she loves Justin to this day, she still has her reservations about getting back with him. He would have to lose the friends that have a checkered past."

But Bieber appear committed, and not willing to take no for an answer. Word is he has been constantly texting and calling his ex, making sure to give her plenty of flirty compliments.

The next step for the lonely Bieber seems to be convincing Gomez, who recently split with boyfriend DJ Zedd, to see him in person.

"He has plenty of people around him but not many that he's emotionally connected to," the source added. "He asks her to come over, or suggests they meet up somewhere secretive, but she's not falling for it. Selena isn't biting so far and has no plans on meeting with Justin."

But how long will she really be able to hold out?