my best friend and halloween

[Haunted]

this is a quite stupid thing and again I don't know if this is the right place to post it. Tell me if I have to move it.

To understand what happened, you have to know:
my best friend changed school. She went to school with me last year, but she had to change and now she's still in 1st grade in high school while I'm in 2nd grade.

Everyone knows that in 8 days it will be halloween. I wanted to meet my best friend and have some fun together. I was thinking of fancy dressing, eating something together (like pizza) and maybe watching a film afterwards.
But she told me her classmates invited her to the cinema and she wanted to go. She told me "maybe we can meet on saturday".
I didn't want to sound lame so I just said "oh, that's okay then", but I was thinking "You've known me for more than 10 years and for the past 5 years we have always spent halloween together and now you leave me alone because you want to hang out with people you've known for less than 2 months? That's quite unfair, girl!". I mean, if I had someone else to spend halloween with it would be okay. I still would be quite disappointed, but I wouldn't really care.
At the moment I was feeling really unimportant. She had never done something like this to me and she even knew that I had no one to spend halloween with because I had told her about that.

What do you think? Am I right or a I just behaving like a stupid child?
And shoudl I tell her something about that?

[PSY]

Traditions are important, so I can understand why you would be upset. There are two things you could do:

1. Explain that you really enjoy your tradition with her, and would love it if she could hang out with you before or after the movie with her other friends.

2. Meet with her on Saturday, or another day. (Because ultimately, it's not the day of the week that's important... it's the fact that you're spending time with your friend, on ANY day of the week, that's important.)