I had a somewhat similar situation happen to myself, but I was the one being accused. I can relate to his defensive and occasionally aggressive behavior because when someone is constantly accusing you of cheating on them, it is draining.

Being called a liar when you’re telling the truth and have done nothing wrong is disheartening. He’s human as well. If he constantly accused her of cheating even after previous denials, she would snap as well.

As far as the social media aspect of liking pictures, everyone is different. Some people see no harm in simply liking a photo while others see it as flirting. If she hasn’t, she should be clear it makes her uneasy and if he cares about her to ditch the likes so she can stop stressing about it.