A bit off topic but I can understand why she was charged with manslaughter when it should have been arson, it is very unfortunate that the man died fighting the fire but she didn't set out to kill him, and this is on the same day that the knife boy in croydon gets a two year suspended sentence.
Involuntary manslaughter occurs where a person kills, but does so without the intent to kill or cause GBH.
There are two types of involuntary manslaughter, namely:
that caused by the defendant's gross negligence; and
that caused by his unlawful or dangerous act.
Basically, if you recklessly perform an unlawful or dangerous act and someone dies as a result, you can be convicted of manslaughter.