Actually it's a little more complex than that. Context is very important. Lay people read law and interpret it verbatim, and unfortunately that's not how you actually decipher law.
Intent is still actually a part of manslaughter, just not deliberate intent as in murder.
The intent could be described as "someone creating a perilous situation with the capacity to cause harm to another person, when they should have known better to prevent that situation."
There is nothing perilous about being on a large balcony, either sober or drunk. The railing is safety approved, this alone is legal exoneration from any culpability.
The most common manslaughter scenario is killing a passenger when you are driving dangerously. If you wish to draw a parallel between a driver in that context, and a person who withdraws from the presence of another by separating himself from the other party via a glass door , well, that's drawing an awfully long bow , the likes of which has never prosecuted in an Australian court of law.
The prosecution has to prove the deceased was in fear of her life. On the facts given in the news reports, it's simply not provable. It would still be potentially hard to prove even if there was a direct witness, depending on the evidence they gave, which might very well be a personal opinion. Everyone wants to believe fear of attack was the causative factor for the decampment over the railing, however given the state of inebriousness of the party concerned, the prospect of it being something else such as hallucinogenics or similar, is very real.
In other words, there could be other reasons for the decampment. Not just the one you all want to run with. The court will examine all the possible reasons, not ignore them.
One also needs to understand that adults are not defacto nannies for other adults. You are essentially responsible for your own choices, even still to a degree when you are drunk. If I am walking down the street, and I collide with a drunk and berate him, and then he steps out into traffic and gets killed, do you think I am culpable ? No.
If you really want to know what gets prosecuted as manslaughter, go and research some other cases. It is never anything like this case. On that basis, these charges seem to be a total non sequiter. As it is these days, Police will charge anyone they don't like on a whim.
