In order for your daughter to save her marriage, she needs to end the affair and cut all ties with the third party. Remind her that she'll have to be be completely honest with herself from now on. It's impossible to rebuild a marriage after an affair if you have anything to hide, warns psychologist Dr. Phil in the article, "Advice for Cheaters and their Partners" on Dr. Phil. It will never be a "good" time to tell her husband about her affair, says couples counselor Elly Prior in the article "Surviving Infidelity" on ProfessionalCounselling.com. Be your daughter's sounding board as she works out how, where and when to break the news. Prepare her for her husband's reactions, such as anger, sadness and frustration.

Your daughter may feel that her marriage is over and she wants to continue with the other extramarital relationship. However you feel about this, it is her decision. Do not try to talk her out of it, but help her see things rationally. Ask your daughter why she wants to leave her husband. She may feel that her marriage no longer satisfies her or enhances her life. Point out that marriage is not easy and all couples go through rough times. Remind her that the "honeymoon stage" of a new relationship and the excitement of an illicit affair is not representative of a long term, committed relationship. If she is absolutely sure there is no hope of recovery, she should end her marriage gracefully, advises Prior. Talk to her about the strong emotions she may feel, such as guilt, shame and disgust. It may take time for those feelings to subside.

Your emotional support will help to boost your daughter's strength and courage, which she will need to resolve the situation, whether she decides to rebuild or leave her marriage. Many people in her life may disapprove of her behavior and align themselves with her husband, so she may feel isolated for a while. Visit her regularly, and keep in touch by phone and text when it's not possible to see her in person. Make sure she is looking after herself, both emotionally and physically. If your daughter decides to leave her husband, she may require practical support, such financial assistance, help with childcare or a temporary place to stay.

Counseling may help your daughter deal with the problems in her marriage and cope with the fallout of her betrayal. Your support, plus that of other family members and friends, may not be enough to help her recover from this crisis, says therapist Julia Flood in her article "Can You Really Get Past an Affair" for eHarmony. Help your daughter find a suitable qualified, experienced therapist in her area. GoodTherapy.org, founded by licensed family and marriage therapist Noah Rubinstein, lets people search for therapists by zip code, state or type of therapy. If your daughter and her husband are equally committed to making their marriage work, they may find it productive to see a marriage therapist together.