Did you just wipe it off quietly hoping for to not notice or did you make a production out of it? If you made it a point of contention, that may be why it escalated. If you just quietly did it and she took offense, that's a bit overboard.
Regardless, best of luck comparing your actions to your wife's mothers. That should win you a lot of arguments.
I didn't make a big deal out of it at all, I went to wipe it off, not dramatically, and she said "O MY GOD, JUST EAT IT!"
That's when the argument broke out...