"You've changed me forever. And I'll never forget you," the message reads. In the caption, Bella simply wrote "8/9 | 6."
While the first numbers refer to Thursday's date, the "6" could refer to her six-year relationship with Cena.
The post came just a few days after Cena tweeted about trust in his own mysterious message.
"Trust is a powerful thing. 'Don’t trust anyone' closes the door on the experience of life," Cena wrote on Aug. 3. "Learn to trust people, good and bad can come of this, but the more you trust, the more you get to know people for who they really are."
"People will speak about you. People will try to speak for you. People aren’t you. YOUR voice is the most powerful when it comes to your values and beliefs. Always be accountable for your voice, and sometimes the best use of it, is silence," he wrote in another tweet on Aug. 2.
Cena and Bella were set to be married in May before they called off their wedding. There was buzz about the two getting back together, but they recently split for good (until the next time they get back together).
TMZ reported late last month that the two WWE stars told friends they are no longer together and grew apart while Cena filmed a movie in China.
The marriage's cancellation was the focal point of the Total Bellas season finale, in which audiences saw Bella explain her decision to her family.
"It's tough, because he's fighting really hard for me. There's something that is making me not feel like I can walk down that aisle. And that doesn't mean ever with him, I just can't do it right now," Bella told her family.
Bella said she still loved Cena, but did not want to be in a marriage that could be unhappy because of a desire to please others.
"I didn't give myself long enough when we called it off the first time," Bella said during the finale. "I just realized there's deeper problems. To have a happy, healthy lifetime with him, I have to take a while for myself."
In a July 30 tweet after the finale aired, Cena tweeted, "If you can learn something from your experiences, good and bad, you will live with little to no regret."1comments
Earlier this week, E! Network announced that Total Bellas was renewed for a fourth season. The series co-stars Bella's twin sister, Brie Bella.
“I can’t wait for our fans to join me in the next step of my life," Bella said in a statement. "I promise that it will be a fun, real and heartfelt adventure.”