Why did she do it? If she was drunk or he was an ex, etc... that is one thing and forgiveable to a certain extent.
If he was better looking than you and had a bigger dick, death is the only option left on the table for you in regards to her.
Preferably her death, but only after you get his pics off her cell phone and post them here.
I disagree. Not forgiveable.
In any circumstance, not forgiveable.
Even long-term.
There are so many opportunities to change your cheating mind before doing the dirty deed, There is really no excuse for following through on poor judgement.