Jealousy at its finest.

My boyfriend has an ex he's still in contact with. He doesn't flirt with her, he doesn't talk to her unless he needs to, but SHE contacts HIM whenever. She snapchats him, comments on shit and likes all of his pictures on social media. It honestly pisses me off so I confronted her about it. I was very calm and nice and she seemed like she understood and said she doesn't have feelings for him, but she continues to do the same shit. I talked to him and told him how I feel about all of this and he held me and told me there was nothing to worry about, kissed me and told me he loved me. I trust him with everything I have, but I'm honestly going to end up beating this girls ass if she doesn't stop. Advice anyone? Am I overreacting?