I 20M and my girlfriend 18F had a big fight because of my insecurities (needs help)

I and my girlfriend have a beautiful relationship of 4-5 years. Recently On my birthday Our friend group (4 friends) decided to go to a restaurant to eat . At the end time one of friend cancelled so it was just me and her and our common friend (a boy) . While going to hotel she travelled with him and also while coming back. Also in restaurant they sat next to eachother. That boy is our common childhood friend. Recently he confessed her that he had feelings for her . So I was not loving what I was seeing they both were enjoying eachothers company .I started to feel lefted and went silent (I usually don't talk very much) After eating we were clicking photos. She remembered a reel and wanted to recreate it . It was a couple dance reel And she wanted to recreate it with that that made me even more uneasy and insecure or jealous I don't know I just had this very uncomfortable feeling.They practiced and I was the one shot there video .All of this things were kind of angered me . Yesterday I told her that I was not happy with what happened there I was telling her that you should have some limits if the guy likes you . She agreed and said sorry but ti was still unhappy so I was still silent than usually I am . And then She got angry that I always hold up to thing's and can't let go things easily. I told her that's how I am I can't just forget what's bothering me for so many days.She said that it was a very little thing and doesn't matter at all . I just danced with him and you should not take it seriously and also don't take the boy seriously. I said what of I did this . She said she will be ok with it .(I am sure she will be not ). I told her that you are this confident cause you know I will never do this (I really don't have any other female friends except her ) and she got more angry she confessed that she don't love to share everything to me because of my this behaviour of not letting things slide or holding to small things like this .

I don't know what should I react I just told her that now I will not react to anything. She has alot of male friends that's ok but sometimes I think she should have some limits with them but then she thinks it's all very small things and I am making an issue with this . I now that she said that she doesn't share with me because of my this behaviour I don't know what should I do .(Don't misjudge her character because of this she a lovely girl it's just that for her it's all normal and for me it isn't I haven't socialised much since my childhood I had very less friend and a strict environment)

Ps :- that guy doesn't know about our relationship