a) If a girl feels it first, she should say it first. Honesty is important in a relationship. And I've heard of no "conventions" on this point.
b) As the Smiths said, "How soon is now?". If you feel it, then it's not "too soon", people have loved at first sight before now (myself included). So no, by any definition it isn't.
And no, the fact you're both 22 makes no difference.
Tell him...if he's worth loving, he'll be delighted.