everyone on here will be the first ones to tell you that Disney is the most awesome place and can never really truly understand someone would NEVER want to go. while my first reaction was just like everyone on here (dump her) ask her this....what is it about Disney she isn't willing to do? does she not like the crowds, long lines, the food, the rides....what is it? second, if she is so into you, why is she so unwilling to see something through your eyes? maybe the people she went with didn't know how to do Disney right (let's face it, we all think we know how to do it right!) and finally, how would she react if you went on this vacation without her. if she can't give you honest answers for any of these questions including how she would react if you went alone THEN I say she's got to be ditched.
I agree, if you were asking her to go bungee jumping I can see her being hesitant, but it's a freaking amusement park (ok the ultimate park, but still) it's not a suicide mission. and to me, someone that doesn't want share something that is special to you doesn't really deserve to go to the happiest place on earth....