This is liable to make you laugh more than her, but in the Knock Knock joke vein you may want to try:
"Hey, I got a good knock knock joke. You start it."
Better yet, ask her if she ever ate cow milk or chicken eggs, and while you do so, make a face that expresses disgust.
Chances are pretty good she will protest that she has never done such a disgusting thing.
Once you explain the "joke" she may not laugh hysterically, but she will be hel bent on trying it out with her friends (Just like the knock knock joke above).
What's better, a belly laugh from your joke or the satifaction of knowing that she will feel wonderful pulling a joke on her friends?
If you just want to make her laugh, act like a complete idiot.
No joke is needed.