I dont consider myself to be an extremely jealous person but I am pretty intuative in noticing when someone is attracted or interested in the person I am with. My fiance had this one coworker who would  stop by her office, ask her to go to lunch, complain about her relationship issues, ect. From the beginning based on what my fiance shared I just felt this person liked her. We went out with this coworker and her gf a few times and the interactions at first felt awkward. It also turned out that this persons gf looks very similar in appearance to my gf (which reaffirmed my suspicion she is attracted to my fiance). I have had several conversations with my fiance about how I feel. She has set stricter boundaries with this person to respect my feelings. My fiance tends to be very friendly and caring of her friends and I dont have any suspicion that she would or has cheated on me but I still feel jealous of this person. Now this coworker has started a new job which i thought would be a good thing but now she texts my fiance all the time to the point that I am getting very annoyed. My fiance and I face time while at work often and it seems like everytime we do this person is sending her messages on facebook messager as well. ( I know this because I hear a constant ping and my fiance told me it was her). I feel as if I have reasons to be upset but I dont want to be a nagging jealous girlfriend. I have thought about why I feel jealous or threathened by this person and as much as it hurts to admit it:  she is attractive ( as am I lol ) , she is outgoing (which I am not), she is very open about her sexuality (im still a tad closeted), her family is very accepting ( mine is not which puts a strain on my relationship). I know my fiance loves me and like I said earlier I dont she has or would cheat on me. I just dont know how to come to terms with these feelings so that they dont affect me as much as they do now.