Harassed by Ex-narc new girl

Hello all,
I wanted some advice on how to feel about something that happened recently. I was recently harassed and had to block my ex-narcs new girlfriend on instagram. He walked out on me about a year ago this July. I have not seen or had any contact with him, his family, or his friends since that time. This is the girl he cheated on me with and left me to go be with. This is also the same girl who he had contact me and rub their relationship in my face when everything was going. It was nothing but a giant kick in the stomach. I only know its her because I saw pictures of the 2 of them.
I did not go through her pictures, I left her page as soon as I found out it was her. When I posed a picture of a quote alluding to me knowing she was watching my page. She sent me a message request on instagram as well. I did not read it and I denied the request. I guess she realized I denied and wasn't going to respond to her so she started going through all of my pictures liking them, and leaving comments about how I am not over my ex. I blocked not long after she started this nonsense.
I was shocked that she found me on social media because my ex doesn't use it and I only followed his sister, of whom has't followed me since we broke up. Not only am I not sure how she found me, since his family doesn't seem to care enough to concern themselves with me and my pain even though they all loved me at point. I am also shocked that after 1 YEAR, I am still a thought and on anyone's mind over there. I have heard a few things like they probably aren't as happy as they seem, and that he is probably cheating on her and she thinks its with me. I have heard maybe she is miserable and wants to see if I am too.
Now although it did hurt to see them together, it wasn't as bad as a year ago. I am a lot farther a long in my recovery but certainly not all of the way healed yet. I honestly am hurt to think of the possibility that he could be behind this or his family. That they care so little that they would try to hurt him and bring me back down. Luckily my social media has been very uplifting and positive and full of pictures of me having a good time.
I wanted to know what you guys think because I don't trust my own instincts as I am still wrapping my head around their ways. Please help me get through this attempted set back.