I've been watching BB since series one, I've never seen them edit things like this, I.E. in a non-linear way.
Tonight we saw the warning first then the offence in flashback. {they have occasionally shown flashbacks if something sparked a day pr two later in relation to an event but never the same day before.}
But I have a theory.
I think the spitting was so revolting and unacceptable that they needed to demonstrate their OWN action, in reprimanding her, first.
They show the warning then show the offence. It is a way of appeasing the general public, if you follow me.
Had they shown it in a linear fashion the audience would have gone potty.
Part of my theory is also that they didn't see it or stop it happening at the time, so needed to demonstrate FIRST to us, the audience, that they 'dealt' with it.