OK, there appears not to actually be any such word as "seriosity", no matter what Urban Dictionary says, but there should be: the state or degree of seriousness of an individual or situation.
One of Katie's many strengths was her ability to laugh at herself, to not take herself too seriously. I'd say her "seriosity level" was (appropriately!) low. That doesn't mean, of course, that she didn't take anything seriously: rather, she could see the funny side of things, and if that meant poking fun at herself, then she was fine with that.
The flipside of low seriosity is the risk of folks taking offense. It seems to be in vogue nowadays to take offense at just about anything that makes a joke about anyone. While of course there are times and places where jokes are inappropriate, the fact that a joke is made doesn't automatically mean that it's always reasonable to take offense.
I've laughed at jokes about suicide, even after November 2010, because they were funny, damnit. And I know Kt would have done the same.
So that's a long preamble for the following, which I know she would have laughed at, and which will no doubt offend a few folks: