<human>: Can you give me a shortened version of the text?

There is this girl I've known for a while, but she went to college to another state. For Christmas break we planned on going on a date. I told her a specific day we would be going out and she agreed. 

Two days before the date I sent her a Facebook message to confirm the date. She then answered saying "It's my siblings birthday that night, maybe another night if you are free?" 

I am not upset she celebrates her siblings birthday, but at the fact that if I hadn't messaged her, when would I have found out that there was no date? Makes me feel that she doesn't care as much, but am I just being selfish? Should I give it another chance?

I am 22 year old guy, she is 20. Thanks!
<bot>: She cancelled date when I messaged her (for a legitimate reason), but what if I hadn't messaged her, when would I have found out? Should I be upset or give it another chance?