Bitterness

Have you ever had someone you loved? This was many years ago... yet is still sticks with me, all the memories. We were teenagers, we were bffs in a boy/girl kinda way. I was her protector, she was my sanity.
We had some fights, disagreements, and some rough times and some great times. We kept the standards, and still dated other people. I went over as soon as I got my braces off when I was 16 to show her. "Wow, ya got no teeth!" she said. I still laugh about that.
We did Prom, Homecoming, even my first date. And yet, I have learned that my sister is right, yet again.
You see, after we finished high school, she moved to Utah to go to school. Okay, this is not uncommon. Contact began to wane, and then I went on a mission, so it pretty much stopped completely.
She got engaged. Okay, so what? I've moved on with my life. I was planning on marrying someone else even before I left to go serve.

But when I was at someone's house last evening, and saw the announcement on their fridge, I was just a little bitter. I didn't say anything, and I have only spoken about it to my family. But this one is going to take a while to get over. Not because I "still love her", or can't "get over her", or anything like that, but she didn't even have the decency to send so much as an announcement.
Am I incorrect in this? Or is this okay?
Tell me what you think.