Reader Question Wednesday: Who Is Telling The Truth?

Hi.  I have always had a super competitive relationship with my twin sister.  She has been known to be, for lack of a better way of saying it, “the bitch”.  She was the Queen Bee in high school and college.  We fight and she is more competitive with me (I always have stepped down a bit and let he have the spotlight as that has never been very important to me).  We are close as well and love each other.  However I am engaged first and her boyfriend won’t even live with her.  She sat me down the other day and told me that  my fiance hit on her and asked her to have an affair on the side (that to be in a secret affair with a twin would be really sexy).  I know we are competitive and she likes to win, but I never in a million years would believe she would take it this far!  And I never would believe my fiance would do that.  I confronted him and he swears up and down he would never ever have done that and that she is just jealous.  I really really have no idea who to believe and the loss of either makes me sick.  Any ideas?

Torn, Virginia