You cant go back and change the past. So you either let it go, forgive her and move on or you break up. Its really simple. But a lot can change in a year and s**t happens. You were apart. She could have been seeing someone else for awhile.. most single people are looking for love so what makes you think she should have waited around for you? She likely thought you were never getting back together.
She shouldnt have lied but she was prob scared of your reaction.