Knowing how to break up with a cheating girlfriend can do more than free you from a relationship ruined by betrayal. You can break up with her the civilized way or you can make a big exit, humiliate her and send an equally hilarious and ominous message to other cheating girlfriends out there. How you break up with an unfaithful girlfriend is your choice; she chose to betray you and you can choose how to set yourself free.
Take the gentlemanly way out. Sit her down in private. Present your girlfriend the proof you've collected that she's cheating on you. Calmly and firmly explain that her actions are not only treacherous and evil, but that you don't like being taken advantage of. Worse yet, she has also put you at risk for catching any venereal disease she might get as a result of her dishonesty. Explain to her that this is why you can no longer be with her and tell her it's over. Either it's time for you to move out or she's gotta go. If you live apart, give her back her stuff and delete her from your phone while she watches. This should be done in carefully measured steps, so just in case you're wrong about this, you have a snowball's chance of undoing the mounting damage.
Public humiliation. Break up with her in front of her co-workers or friends and say why. Sometimes they actually know she has been cheating on you and whether they have her back or not, they know deep down she had it coming. Since moves like this pretty much kill a relationship far beyond any hope of recovery, this should only be done after, say, you actually caught her in the act or she has confessed.
Be impersonal. Revenge is sometimes a dish best served cold. Sometimes the impersonal touch can hurt even worse than embarrassing your cheating girlfriend in public. Break up with her via phone, text or email. Have your friends pick up her stuff for her and take it out by surprise when she's not there and then change the locks, if she's not actually living with you. Again, this is pretty brutal and should only be done when you've caught her red-handed or she's admitted to the deed.
- Never just change the locks on your cheating girlfriend and confiscate her stuff. The law will have to get involved and it would see her as the victim, not you.
- Never confront her other lover to tell him she's cheating or confront her in the middle of the act. This could lead to violence.