Dealing with anger in a relationship?

ok so im a 17 year old male. ive been with this girl for 9 months and things are just starting to get bad. she always seems likes shes flirting with guys and at first i thought it was jelousy getting to me but then i realized she only does it with the people she constantly talks about or people she knows like her. i get really angry and it starts a fight everytime. the thing is it wasnt always this way, when we first started dating i danced with another girl and she freaked out and talked about how hurt she was. i didnt think there was anything wrong with it but i stopped anyways, next thing you know 9 months later shes dancing with all kinds of guys and im under the impression it means somthing cause she said it does. we took a break cause she said i need to find a way to calm down and deal with her basically. ive talked to her about slowing down the flirting a little and how i feel about it but shes under the impression letting other guys pick her up and tickling her or slapping her but is just play so its out of the question... i really love her but what should i do to deal with her flirtatious attitude? im trying to just accept it cause i figure it will be worth it but i need to find a way to stop yelling. do you think this is the behavior that would lead to her cheating? and also, if we are on break ive mentioned seems were not quite broken up she shouldnt have this guy that she used to like walk her to homeroom math and art EVERY DAY. does that seems unreasonable to you? any advice would be liked pleaseDealing with anger in a relationship?
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