How is she a scum bag?

Because if she didn't seem to care about the guy cheating, it's more than likely that she knew about it.

It never suggested she didn’t care. I think personally ending their affair when you immediately find out about it is a pretty normal first step.

Side note: Knowing or not caring about her boyfriend sleeping with someone else still doesn’t make her a scumbag.

The other girl broke up OP and the dude, not herself and the dude. That does imply that she did know and didn't care.

And yeah, it kinda does. Knowingly participating in someone else cheating is just as bad as cheating yourself.

You’re reading into the situation and claiming this woman is a scumbag based off of nothing other than the fact that she separated her boyfriend from his side piece. Makes sense.

If she's the one who knew - then she's the side piece.

It appears this discussion got derailed by bringing in the hypothetical situation of whether or not she knew. Let’s just strike that from the record and work with what we DO know and... (reference my very last comment).

Yes, let's go with what we know from the FML. That being that there's even less evidence to suggest that she didn't know, as there was no mention of any sort of surprised reaction. Though, if we just take everything at face value and don't imply a single thing, then we are both incorrect and this conversation is ultimately pointless.