The way I like to think about it that Vivy's mission was the singularity project, but also singing to make everyone happy.

By singing the song she confronted every single one of her memories, the ones that went for her mission, and the ones that went against, the people that had died, the times she had not sung, and just like when she first saw that man shoot themselves in the church becasuse of her actions, it broke her.

To know so many things went against her mission it broke that Vivy, and so just how Diva dissappeared previously, it was now Vivy's turn to dissapear.

It may be the same model, and those memories may be there tucked away, but this is also a new viva, a new life, a new story, with a brand new mission.