Reject My Alpha Mate

Sianna rejected her mate for her sweetheart Curtis, as they had promised to choose each other to be their mate. But Curtis failed to reject his mate and lied to Sianna instead.
Anger drove her broken heart to fall into her ex-mate's arms. They had a steamy night, but god, why she never knew her mate was an Alpha!
And now the Alpha would never let her go. What should she do?