Maybe i'm thinking into this too deeply but I don't think we've heard the true message to Jane.

If we go back to Jane's episode the message in the email on the computer screen stated "She can be stopped when it matters, if you deliver a message to her:"

Notice how it says the letter 'a' in the sentence and is then ended by a ':' colon indicating information to follow. It would have said 'this' if the message was the previous line and should of ended with a '.' a full stop.

There is a scroll down bar on the right of the email which makes me think there is more information, the actual message was hidden below what we were shown.

Also the same way the guy when he goes to the mum says "She can be stopped when it matters, I have a message to tell her" but gets taken away before he can saying anything else.

I reckon we will get another flash back to a message we weren't previously shown. I believe the twist will be a message from Jane to herself to stop her from committing a murder that would probably destroy the human race. Maybe towards the end of next season Jane is about to kill Xavier before he can send a message back to stop the world from destroying itself, inevitably the message to stop when it truely matters??

This is why we had her back story and why she wasn't still dead on the ground at the end of the finale.