Side Chick

My SO & I had issues in the past before that has led to trust issues. He cheated before about 5 years ago. He and I separated for a while but have gotten back together and have been going strong ever since. Now all of a sudden, his old side chick keeps popping up on his social media with all of these flirty emojis and telling him how good he looks on his photos. She is still around because she is related to one of his close friends so she comes around for events and things. At first I didn't get upset because he can't control what she does. But this is about the third time she's done it and it's starting to bug me out tremendously. He never responds to her, but am I wrong for feeling this way knowing the past that they shared. I feel like we've come a long way dealing with our trust issues and I'm not trying to go back to that space. I'm not trying to be insecure or anything but the situation is just rubbing me the wrong way. Would you ladies like some old side chick flame flirting around with your man even if he's not responding or what you address it?? I went to leave a comment on his photo and the first comment was from her saying "😍😍😍😍 Well damn. My goodness". I don't know if she's playing around or not but it's annoying me and making old feeling resurface to the point , I'm not trying to be bothered with him. Is it best to address it or let it go ? ? ? Am I looking to deep into it.