Kudos for not caring what other people say, but your right when your bf says junk about you, it hurts. Plain and simple it's wrong of her to assume you cheated and especially to spread rumors about you. She's obviously too immature by gossiping and spreading rumors and will likely do it again. If you want to send a clear message to her, give her the cold treatment. Stay away from her so she knows that you didn't like what she did and will have more respect for you in the future. If she doesn't come back with an apology then it means that she didn't care about your feelings is obviously not worth any of your time.
learn how to speak english you retard