Sorry to hear that My sister slept with one of my exs quite afew years after i dated him tho wasnt bothered at all and she also dated another of my exs but we wasnt serious so wasnt serious so suppose doesnt matter and shes flirted with afew all but one revealed they liked my sister more than me talked about her all time to me like your sister seems very sexual not like you your sister has a better figure your sister wears better clothes and is better looking .