Is she making a huge mistake leaving ?
Possibly, probably ... however, if they play it right and she changes her mind and comes back later, which she could do provided they don't kill her off.
The obvious thing for them to do is have her move back to Massad with some type of job there, this way if she does change her mind they can bring her back ... Wish the would have done that with Kate, it would be great to have Kate come back to the team .
She could be making a big mistake if she doesn't have things lined up for after she leaves.
She could just be burned out on it, never know, needs a change of scenery.
Maybe she is tired of talking in a fake middle eastern accent? Maybe she is tired of Tony snooping around her like a dog in heat? Or maybe she wants to start a career in movies? Or it could be she might have made enough money over the years & she wants to drop out of the limelight and "retire" from the public eye.
Me read that they were going to TVLINE | You previously said that we would find out what Ziva and the others were up to during the four-month time jump. Will Ziva's story now be different?
Basically, the Ziva story sort of intertwines with where we left Gibbs off at the end of the season, with the sniper rifle. That whole story arc unfolds through the first episode, and then Cote/Ziva plays very prominently in the second one. There's a really significant Tony/Ziva payoff — everything I hope the Tiva fans have been waiting for.
TVLINE | Oh, but I can't imagine it's much better than heartbreak for those fans and for Tony.
It informs her in ways that I think the fans will enjoy. It gives us some insight into this decision that she's going to make. It's exciting. And it's romantic.
TVLINE | Is Tony the first person she shares this "decision" with?
Oh yeah. Look, it's a storyline that I took very, very seriously — I felt like I had to, for the fans. I recognize what this means to them, and I recognize what her absence is going to mean. Someone asked me what I plan beyond this, and I can't replace her. I can't even use the word "replacement" for Ziva and what she means to this team. The only thing I can try and do down the road is come up with another character who feels organic and fills a void of some kind.
also I think Piper Perabo would be If Covert Affairs would be cut or Finoa from Burn Notice sinceit is ending would be good replacements!! imo 
