Do you think it is sometimes better to hide the truth?

In the case of a couple who have been together for 12 years and the wife cheated on her husband once with an old flame. She knows she will never do it again. She asked me for advice and I said it is better to not tell him, all it will do is cause problems and since she has no intention of doing this again I think it would do more harm than good if he knew. They have young children and he is a really nice guy but was not making his wife feel particularly wanted and this other guy flattered her, this is why she did it - she knows its not a good enough excuse but she cannot erase the past. Do you think I gave the right advice?