how do you deal with a betrayal?

Throw them to the curb and move on..

Feed the betrayer to the wolves.

Deactivate them

Pick yourself up, look in the mirror and remember that the best revenge is living well.

that would all depend on the level of betrayal and who it is/did it
did they steal your cookie, make ya loose a million $ , did they tell lies so your wife / husband to make them leave etc etc

the majority of my time , its not worth wasting time on it

1 you take the chance of doing something you will regret/ cant take back later
2 they are not paying rent , kick them out of your head and move on (its changing you hanging on to it)
3 you are bringing yourself to a lower level and are wasting time
4 very strong chances of repercussion , you might get put in jail or find ya self in the middle of a war (your friend / there friends / hire hands) , etc etc etc

there's just a few for you
it more or less goes with who you are and what you want to stand for
sadly with as complex as humans are ... it would end up on my list of WTF and ones to be avoided, but again it all depends the level of betrayal
as much as i get called a monk because i am a patient person , even i have my limits
<shrug>

It does time to trust again after being betrayed.