The plot of this film

She was pushed off the balcony accidently during a violent arguement

There is no absolute visual resolution. It looks like she simply falls without Rojak helping her. It's ambiguous. I suppose the confession is out of guilt. OR - and if this is right it was not even hinted at - Rojak confessed to be safely in custody and out of the mob's reach.

Rojack's approach of her + putting hands upon her gets her up on the ledge. She starts to fall of her own momentum (and inebriation), but Rojack "kills her" only in the sense that he willfully fails to reach out and pull her back. Slippery slope just how much culpability he has.

What really gets me is Rojack's dialogue

"No Deborah. You Fallllll"
or
"No Deborah. You'll Fallllll"

AS HIS WIFE IS FALLING.

It not only sounds ridiculous, but who has the foresight to think (on the spot) to
(a) provide exposition to a doomed person (who can't hear you in mid-fall anyway)
(b) think of dialogue that (if overheard by Ruta) will support a false claim of suicide

That (b) option could only form in Rojack's mind in the immediate minutes or hours after the accident happened. Nobody thinks of that in the moment.