well sort of but a little more intense.
my ex-bf (from like 4 years ago) cheated on me WITH my friend and then I broke up with him and they started dating like 3 days later.
I didn't really care though because I kind of fell out of 'like' with him and they were better for each other anyway to be honest.
They dated for almost 2 years and now she's a lesbian.
That's gotta be a bummer though Cassidy.
You can do either one of two things...if you genuinely like her & care about her make sure you have a serious talk with her about how he cheated just so she's clear about what happened and she can look out for it. (I'm sure she won't listen...but you should just try anyway)
OR if you're mad @ her/don't really like her you could just laugh quietly to yourself....once a cheater always a cheater they say. hehe
Just don't let it bother you too much, at least you're rid of him now.