Personally: I think an Insta "like" has such different value to different people that it's basically impossible to interpret what that means (for your relationship) without discussing that with the other person first. Or at least looking at what their regular behaviour is (do they follow 3 people and like almost nothing or follow 1000 people and like everything that passes under their thumb?)

Then there's the whole aspect of guys looking at other girls than their girlfriend. It shouldn't matter, but it does. How do you deal with that?