She was just letting off anger/steam.
It's not serious, she's not going to act on it.
Like Dinh humorously put it, she probably forgot about it the second she left.

Plus speaking as a fellow Canadian, you're even safer than in most places.
Canada is not a violent place, you'd have to be in the center of toronto or ran into the rare "expelled delinquent" person to feel your life is at risk.
And I highly doubt she's an expelled delinquent, and if you're in Toronto... well she's not one of the people that makes toronto more risky anyways. :P

Death Threats actually being acted upon are an insanely rare thing anyways, are normally well planned out and/or done in response to serious trauma such as constant bullying at school. Not over something small like a spilled coffee.

As for if I myself got a death threat? I probably did at some point, but stuff like that doesn't phase me. I just tune that stuff out as the person being a prick and move on.