Dear Margo: A few years ago, my husband of 15 years started an affair with a girl half his age who lived with her husband and child just a few houses from ours. They not only cheated, but lied about it for months and joked to neighbors that they were involved. I knew it deep down; I just couldn't face it. Prior to this, I trusted my husband.

Well, the girl broke it off and moved away. Then my husband made a promise to make me happy again and work on our marriage. During this time, my best friend needed to leave her abusive husband. My husband and I loaned her money, and she moved in three doors down. Guess what happened next? I saw 250 text messages back and forth proving it. It was like history was repeating, but it felt much worse. This was my best friend, and she knew the pain I'd been through.

Having learned my lesson, I moved out and, two years later, do not regret that decision. My question is: How do you deal with betrayal from people who are supposed to love and protect you? I'm not sure that I can trust anyone. — Trying To Get It Together

Dear Try: For reasons I have never understood, "the best friend" is often the interloper. Just as they say blood is thicker than water, for some people sexual attraction must be stronger than friendship. Think of it as people being conscience-free. Dealing with betrayal is hard. You just have to know in your gut that some people are skunks, but by no means everyone. There are no warranties, alas, about fidelity and loyalty. If you're obsessing about these past events, try letting a therapist help you put the hurt and anger to rest. — Margo, historically

A Drug-Addicted Family Member

Dear Margo: I am 45, female, with two siblings. My younger brother, "Joe," is 41 and married with four children. Six years ago, my husband committed suicide in our home. Joe and his family welcomed me with open arms into their home for many months following the death.

In early 2009, Joe lost his job and asked to borrow money. I was happy to help. He found another job soon after, but for less money, and his borrowing money began again. It was usually a tearful call asking for money for the mortgage or some other necessary expense — always accompanied by the request that I not tell his wife.

Fast-forward to September 2010. I told him I could no longer give him money, having no more to give. Of course, this realization came $18K too late. Talking with my mother, sister and Joe's wife, I realized he was on drugs. The entire time I was giving him money and hiding it from his wife, I was enabling him.

My question is: What do I do? I don't know whether my brother's wife is equipped to deal with this. Joe is not aware that we have all been comparing notes. I want to talk to him, but I'm afraid to tip my hand and tell him that we know. The family cannot pay for rehab. Obviously, my brother needs help, and I think it will have to be in-patient. I have heard horror stories of people going to rehab multiple times but never getting clean. — Desperately Looking for Answers

Dear Des: The family should have an intervention. Do not consider the people who fail. Tell Joe of your fears, and if he wishes to get straight, the family should look for city or state agencies that can provide treatment. Should he resist, family members should go to Nar-Anon so that his addiction will not wreck everyone else's life. — Margo, proactively

Dear Margo is written by Margo Howard, Ann Landers' daughter. All letters must be sent via the online form at www.creators.com/dearmargo. Due to a high volume of e-mail, not all letters will be answered.