Humor is such a personal thing. What one person thinks is hiarious someone else thinks is offensive. I've found that if I stop TRYING to be funny, I actually succeed more often! :-) She may not share the same humor, but I'm sure you do and say things that aren't supposed to be funny that really tickle her. The world is a really random place, and it's good to be able to laugh at it (I think). It's difficult, especially if making people laugh is really important to you, but try to let go of making her laugh, and just be yourself. If you tell a joke that she doesn't get, just make a note of it and keep trying different ones. If it's any consolation, I don't tend to laugh out loud at other people's jokes unless I feel obligated...because that's the weird thing about a joke: sometimes just the fact that you are "supposed" to laugh makes it not as funny, you know? Weird little moments in life that just happen naturally are far more amusing for me, and maybe for her, too?

Does she make you laugh? What does SHE do that you find funny? Why is it so important to you to make her laugh? Maybe letting go of that will help you relax and then the unexpected funny things will come naturally :-)