Have you actually read the lyrics?
There's no shade being thrown at Jessica, I don't where or how you're finding anything from the song that insinuate that they are throwing Jessica under the bus.
This song is more of realizing the damage that had been done and finally understanding that things will change and that they need to keep their chins up and move on with their life.
Yes, I understand that Jessica being gone is sad and whatnot, but what's done have been done. They can't keep dwelling on the past, and honestly it's tiresome to hear people bring Jessica up over and over.