He doesn’t understand why I’m upset

He was following someone from our past that I didn’t like. We had almost fought before because she was constantly antagonizing me and she was trying to get with him, openly. I basically asked if he could unfollow her because it made me uncomfortable, especially after she had texted him for his birthday. He did unfollow her. Now I see that he has her on another social media and he’s viewing her story. His excuse was that he was going to remove her from there as well but he “hadn’t gotten around to it”… I’m just like wow. He’s telling me that “it’s not that serious”. They aren’t even friends so I don’t understand the need to keep her around.