he has also shared laughing & joking with her....but this doesnt seem to be the issue, your issue is a self esteem issue & sexual one.

note this, if a girl in your group likes this girl & she fucked him off... he doesnt think "HA IVE FUCKED HER" he may say it, but he doesnt think it...

he thinks "i wanna fuck her again" but he cant... coz she likes u now.

ur issues are YOUR issues