My understanding is that the State cannot appeal on facts, but it can appeal on sentence. The State rarely appeals a conviction but if there was an error or misinterpretation of the law it can appeal and the sentence changed accordingly.
In general the democracies using variants of the adversarial common law system tightly control appeals on factual matters. So appeals are allowed on points of law and sentence from both sides.
This is because factual appeals would tend to lead to a simple rehash of the case which is not good use of resources.
Now with that said - at least in jurisdictions like NZ and England, limited factual matters can sometimes be heard on appeal
I don't know about SA but an obvious example is some new and important fact.
Also the accused can appeal if he can point to some factor which makes the conviction unsafe. E.g. the Court relied on a factor that it should not have done or made a finding that was not possible to make.
I am not sure any of this helps but at least in NZ i think the prosecution might be able to argue that the finding that Reeva did not scream is one that cannot be supported by the facts.
In simple terms there is no evidence upon which the judge can reasonably reach that conclusion.
In fact, the evidence strongly suggests the exact opposite.
This often comes up with forensics.
You can't appeal a factual finding you don't like - but you can appeal a factual finding that was not available on the evidence.
This actually recently happened in an NZ murder case.