Yeah, I have a female isfp friend who is in an 'open marriage.' She admits to jealousy, although she would never lose her calm, cool demeanor over it, at least not easily. She likes being the most beautiful, the most sought after, and it bothers her that she isn't very sexually receptive, so she's afraid of women who are, and feels competition with that. I've seen her drippingly cling to her man when other hot women are around to assert her place. While she'll express and experience jealousy (in an apparently calm way), she would probably not verbalize it much, but just shut down and close off instead--seek her own avenue of fulfillments.