I say that if she is willing to let you go to E3 instead of anniversary,
and she is going with you, its because
A) She secretly really wanted to go herself and is letting you think you are getting your way when she is really getting hers
or
B) She has something big planned in the future that you will not be able to say no to since she let you go to E3
and if shes not going with you, its because
A) She has something else that she would rather be doing(than spending time with you), and its best that you weren't around for it.
or
B) She has something big planned in the future that you will not be able to say no to since she let you go to E3
and in the rarest of cases for either(which is basically non-existant)
C) She really loves you and is willing to sacrifice something that is for the most part superficial to ensure that you are really happy becasue that is all that matters. You shouldn't have to single on specific day a year to let each other know that you love each other and can & should do that each & every day.
BUT E3 ONLY HAPPENS ONCE A YEAR!!!So I hope it
C in either scenario

edit: changed the word "artificial" to what I meant to type "superficial".