My Girlfriend misses her ex friend.

So the thing is that I have a girlfriend who says she loves me very much and i m deeply in love with her too. But recently she was showing me pictures from her phone’s gallery and i stumbled upon a recent screenshot of a WhatsApp profile picture which was her ex friend’s picture. From her reaction, it felt like she didn’t want me to find it. I asked her about it and at first she was finding words to answer then she said i liked this picture and that is why I took a screenshot of it. I thought it is nothing probably and let it go. Now this ex friend was her classmate and they were friends for over a year before she came into a relationship with me. But then the guy was a bit too much .. like he wanted to talk to her all the time and not have late replies so my girlfriend told me and i suggested to block him if he bothered her. Then She blocked him from WhatsApp and all. But she unblocked him again without me knowing and took a screenshot of his profile picture. She keeps blocking and unblocking him. And today she told me that she called him because she misses him. When she realised that I my mood changed after she said this she said she was just kidding.I don’t understand why I m feeling like this.. i am being insecure most probably.. i just don’t want to lose her.
I want ur perspective. Pls help.