She just couldn't help herself!

Selena Gomez is clearly still obsessed with ex Justin Bieber, because she couldn't resist taking a catty swipe at the Canadian crooner after he defended his new girlfriend Sofia Richie on Instagram. The pop star and Lionel Richie's daughter have been posting a ton of pictures during their trip to Japan, and the The Biebs put fans on blast for making mean comments about his lady love.

"I’m gonna make my Instagram private if you guys don’t stop the hate this is getting out of hand. If you guys are really fans you wouldn’t be so mean to people that I like," he captioned a photo of the pair.

The "Come & Get It" songstress then decided to let her opinion be known by leaving a message in his comments!

"If you can’t handle the hate then stop posting pictures of your girlfriend lol - it should be special between you two only,” Gomez wrote. “Don’t be mad at your fans. They love you," she wrote.

JB didn't take the insult lying down, though!

"It's funny to see people that used me for attention and still try to point the finger this way. Sad. All love," he replied, clearly in reference to SG's shade.

The former Disney star then took their argument even further by accusing him of being unfaithful during their relationship. "Funny how the ones that cheated multiple times, are pointing the finger at the ones that were forgiving and supportive, no wonder fans are mad. Sad. All love," she clapped back.

It's been radio silence, though, since the "Cold Water" singer called out his ex for cheating with Zayn Malik! "I cheated... Oh I forgot about you and Zayn?" he responded.

Selena must have had wi-fi on her flight back from New Zealand, because we caught her landing at LAX on Sunday as this whole thing was going down. She really needs to get a life and move on!