A betrayal of a friend

What can be worse than betrayal of a person you love and trust? To my mind, it is the worst thing that may happen to a person. He/she feels pain and can't help crying.
When you make friends with a person and spend a lot of time with your friend, it is naturally that a person will get a lot of information about you and some part of this information may be secret and sometimes even used to harm you. And some people say that we shouldn't trust anybody and especially friends because they may turn into enemies.
There are a lot of stories that tell us about betrayals of friends. People may hurt their friends. There are people who are friends from childhood, and if one of the friends becomes more successful in life the other friend envies him and wants to have the same as his/her friend. As a result he/she starts to do everything but to get the same as his/her friend and sometimes even to occupy his/her position in the family, at work, among other friends.
Envy is one of the worst qualities that may ruin not only friendship but also love, marriages, and families. It turns a person into a greedy and cruel person who is ready to do everything but to satisfy his/her needs.
Such situations are not complicated from psychological and moral point of view, because they show who is a good person and who is an evil one. But there are much more complicated situations that sometimes happen and ruin even the best relationships among friends.
Imagine the situation that is one of the most spread nowadays. You have a friend, you spend a lot of time together and you decide to present your friend to your husband or wife. And your friend and a husband/wife fall in love with each other and start to see each other. You don't know about their dates and their love and one day you get to know everything. In such a situation you understand that you've lost your friend and your lover at the same time.
Even a professional psychologist will have some difficulties while considering this situation. This situation is very complicated. On the one hand, two people whom you trusted betrayed you, they lied to you, were hiding from you. And it really hurts, but on the other hand, two people love each other and they want to be together. And sometimes people really can't resist such feelings as attraction, passion and love. What to do in such a case? What should they do?
Of course in such a case they should be more reserved and rational. They should consider their feelings and if these feelings are really strong, then they should talk to their friend and wife/husband first. But passion and feelings can't always be controlled. And sometimes people don't think before doing something, they simply obey their emotions.
Nobody can tell you what to do in such cases. You have to decide yourself. In the majority of cases people simply get divorced and break all relations with a friend.
There are a lot of other situations that are difficult to solve. And sometimes betrayal can't be forgiven.