Which is greater: maintaining a pure friendship with someone (of the opposite sex) who I believe has been a dear friend in past lifetimes, or satisfying the insecurity of my fiance by ending all contact with the friend?
This is a question many have faced, and not an easy one to answer. The answer will ultimately rest with you with the help of your own higher self (or guru).
The first thing that springs to mind is to ask what is dharmic (what is right to do)? You have a committment to your fiance that should be very important and primary. Think of ways to build trust between you both. This doesn’t mean you should have to give up all other relationships, but that your partner realizes he is first in your life. You may need to include him in the friendships you have with others more.
If a strong bond of trust does not happen between you and your fiance, and he is overly insecure, you may want to look at this more closely, and help him by suggesting avenues to obtain help in this area of his life. You both may need to have counseling.
Ananda has just put out a new book by Paramhansa Yogananda called How to Have Courage, Calmness and Confidence which gives priceless information and practical help in these areas. We also put out a book called 30 Day Essentials for Marriage.
Go inside yourself, learn to go deep through meditation techniques so that you can contact the inner self and feel what avenues you need to explore to help resolve this situation. Give your fiance and your friends your love.
Joy to you, Seva