I guess there's a lot of options ranging from them having too much time on their hands to hiding relationships from people they know. More importantly.... why are you worried about what your ex is doing?

The moral tribulations of cheaters. Some people have it rough.

A common thing cheaters do is accuse their partner of their behavior in order to justify their own in their heads.

So he's cheated, you want to cheat and the relationship is generally toxic. Why are you still in it?

I never liked the mentality of "if you don't have anything to hide you shouldn't mind if I snoop." There is such a thing as respect and privacy. But there seems a lot of red flags here. Trust is doubly important in long distance relationships and it seems like it's gone.

Tell her so you can both dump his ass back to back.

So she has zero fucks to give when it comes to supporting you and taking a few minutes to read a story that's important to you, but when it's time to fight she's actively pursuing it? That's some messed up priorities.

Removing yourself from an argument and letting the dust settle is perfectly valid. Despite the desire of some to settle things here and there, all it usually accomplishes is both parties saying things they'll regret. Witness your girlfriend's behavior.