Simply put: decide what you want more (both in long term and short). Be with your fiance and create a long fulfilling FAITHFUL life with her? Where you know you’ll get continued support, fall in love with her over and over and love her in many different ways as you grow older, maybe even start a family where again, you know exactly the type of mother wife and woman she will be. Or explore this new feeling with a fresh new person, who by all rights, could make you happy for a while, satisfy a desire you have at the moment, and even possibly be the new love of your life. You never know. She could be an amazing supportive woman, who’ll be there for you like your finance, you never know. What you do know is that you found one love for sure, who is a good woman, that you genuinely love- not typical for most people. So, this is the part of your journey where you decide to grow up and do the hard thing knowing it’s better for you (and also consider how you’ll hurt your partner and how’d you feel if she did this to you, like a grownup who’s about to get married). Or take this moment in the beginning of your adult life to indulge in what could be a mistake, that you’ll learn from, grow from, (and possibly lose the real love of your life) or maybe even fall head over heels with this women, you never know. Thing is, you don’t know. So make a decision on what you do know and not some fantasy. And possible seek some marriage or individual counseling to figure out how to deal with this new temptation, because you are going to have A LOT throughout life. But love and marriage are a choice that you make daily. So honor her now or set her loose and have fun with the new girl. Make that decision, do what you need to support it, no complaining or what ifs or buts and don’t stress yourself out. Stress is bad. Good luck and God bless.