I agree that the writer meant defuse. Confusing that word with diffuse is common amongst journalists and is something that annoys me.
Even so, I have doubts about defuse. I think you can only defuse something that already exists, like a bomb. An outburst, however, is spontaneous - something that happens unexpectedly. So I think it would have been better to write prevent.
She also demonstrates how to read body language in order to
prevent outbursts.
It is unnecessary to add "before they happen".