She doesn’t believe a cheater. She said — Once a cheater, always a cheater.
Cheat on sb. 对某人不忠
She’s been cheated on for a long time and she doesn’t know that at all!
Two-timer n. 脚踏两条船的人
Two-time v. 脚踏两条船
She ended the relationship when she found out her boyfriend was two-timing her.
He is such a player, can't you tell? How many times has he hurt you?
Betray v. 背叛
John has promised he would never betray his wife.