Ariana Grande and Big Sean Dating: Naya Rivera's 'Worst Nightmare' Turns Out True

American actress and singer Naya Rivera is reportedly upset that her former fiancée rapper Big Sean is dating pop star Ariana Grande.

Rivera and Sean first connected on Twitter last year, and announced that they are engaged in October -- just six months after going public with their romance. However, the two separated in April.

Following the split, the 27-year-old, who is best known for playing Santana Lopez in musical comedy-drama television series Glee, got married to Parks And Recreation actor Ryan Dorsey in July in an intimate ceremony in Cabo San Lucas, Mexico.

The newly wedded couple also attended Justin Timberlake concert in Los Angeles, California on 12 August.

"Naya was trying to keep it together and have fun at the concert but she was really upset because of the news about Sean and Ariana. She kept bringing it up," a source told Hollywood Life.

"It's her worst nightmare because she was always sure that Sean was cheating on her with Ariana, they fought about that a lot.

"Sean would tell her she was crazy and jealous, he swore to her that Ariana was just a friend, he even said she was like a little sister. Naya feels like this is proof that she was right all along and Sean was hooking up with Ariana. She doesn't want him back, but it's still a huge wound and she's hurt and she's angry," the insider added.

Meanwhile, a source told E! Online that Grande, who recently broke up with Australian star Jai Brooks, was spotted kissing Big Sean during a movie date.