yo yo, just explain this to her:
"The common denominator of all jokes is a path of expectation that is
diverted by an unexpected twist necessitating a complete
reinterpretation of all the previous facts -- the
punch-line...Reinterpretation alone is insufficient. The new model
must be inconsequential. For example, a portly gentleman walking
toward his car slips on a banana peel and falls. If he breaks his head
and blood spills out, obviously you are not going to laugh. You are
going to rush to the telephone and call an ambulance. But if he simply
wipes off the goo from his face, looks around him, and then gets up,
you start laughing. The reason is, I suggest, because now you know
it's inconsequential, no real harm has been done. I would argue that
laughter is nature's way of signaling that "it's a false alarm." Why
is this useful from an evolutionary standpoint? I suggest that the
rhythmic staccato sound of laughter evolved to inform our kin who share
our genes; don't waste your precious resources on this situation; it's
a false alarm. Laughter is nature's OK signal."
VS Ramachandran wrote this. he is one of the most highly respected psychiatrists/neurologists in the medical world. In essence, we laugh as a reaction to a twist. Something unexpected happens, but we see it as harmless, so we laugh. you didnt expect to see all those words. it surprised you. you realized it was inconsequential. therefore you laughed.
give it a try. good luck