Why would she act normal to me one minute then the next act guarded, distant towards me and try to hurt me by not talking to me and flirt with others?

She would act normal towards me she would laugh and listen intently to me but the next minute she would act distant, ignore me sometimes. It feels like she’s punishing me as she would stop talking to me other times and flirt with others trying to get a reaction out of me?
Why would she act normal to me one minute then the next act guarded, distant towards me and try to hurt me by not talking to me and flirt with others?
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