valid for being upset?

So I was talking to a girl for almost year and I had developed a crush on her, I told her, and she liked me too (apparently)
But after she told me, she kind of just stopped talking to me. And she ignored most of my messages.
And not long passes, and I see she's gone on a date with some girl. And I didn't really care at first it was just, she couldve said that she liked someone else instead of talking to me less, iwouldve have minded and I hoped wed still talk. But now I literally kind of don't exist in her life at all and its almost feels as if I never have. Am I being irrational? Over dramatic?