not sure how I should feel

So my boyfrend and I have been together for quite some time now. I trust him fully but cant help feeling a twinge of jealousy when he speaks to a girl in our college. A bit of background info: me and said girl were quite close last year and I regarded her as a good friend. However, for various reasons me and my boyfrend went on a break and I later found out that my friend had made advances towards him, which he initially agreed to, but after realising he still had feelings for me refused to carry out. We are now back together but I still feel hurt by the situation and slightly betrayed by my friend and boyfriend and i just cant seem to get over it.:[ My boyfrend still speaks to her and I cant help but feel slightly jealous, upset, and slightly insecure upon seeing this. Am I justified in feeling this way and what should I do, if anything?? Constructive advice only please. Thanksss in advance :]

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