Mel B throw a glass of water “AGT” judge Simon Cowell and afterward raged off the set amidst a live show, after he made a reference to an extremely touchy subject … her marriage.

Simon was critiquing a competitor when he started comparing his performance with Mel B’s honeymoon.

It’s just as simple as that … Mel B smiled at first but afterward she was urged back on stage a couple of minutes after the fact.

She’s had an unfortunate separation with her ex husband Stephen Belafonte, so it hit to close to home.

Simon’s still got it.