Selena Gomez could not resist reacting to the recent date between her on-and-off boyfriend Justin Bieber and ex-best friend Kylie Jenner in Las Vegas.

Bieber took Jenner on a public date to the high-profile Floyd Mayweather fight on Saturday (May 3). The 20-year-old singer took to his Instagram account to let the whole world know that he was with the 16-year-old reality star, instead of Gomez. The photo sees the pair getting cozy with each other, posing with model Yovanna Ventura.

Jenner also posted a series of snapshots of herself getting ready for her date with the "Bad Day" singer and traveling by limo to the big event. She wore a lacy black mini dress that showed off the full length of her legs, completing her look with sexy eye makeup, for the night.

How does Selena Gomez feel about this? On the next day (May 4), she posted a photo collage of John Legend's music video for "All of Me," which features Legend being intimate with his wife Chrissy Teigen. "Them is EVERYTHING tho," she captioned the image. Many speculate that this is a way of Gomez reacting to Bieber's recent date by showing him how a real couple should behave.

The "Come and Get It" hitmaker broke up with Justin Bieber for allegedly flirting and hooking up with Kylie Jenner at Coachella. Also, the "KUWTK" star reportedly sent sexy photos of herself to Bieber's phone. "He's saying Selena went psycho for no reason," a source close to Bieber said. "He's glad to be done with the drama, though. He says he couldn't handle her jealousy and insecurity -- it was too much for him."

"When it comes to Justin hooking up with Kylie, it has nothing to do with starting a relationship," the source added. "Justin wants to add to his numbers and conquests and he knows she is totally cool with that."