Well, if she managed to get herself expelled from school -for the heinous crime of being unhappy there?- she must be a murderer.........................apologies to any members who may have been expelled.
The other thing, is that in the 'Sheila did it' scenario, it is her mental state that is being cited as her reason/motive.
So her prior behaviour, which in any event doesn't suggest anything untowards, is somewhat irrelevant.
That isn't the case in the 'Jeremy did it' scenario.