To live is to suffer...

So, I'm perplexed with how some women (made special efforts not to make sweeping generalizations) can without hesitation say that they don't like to be lied to, but do not think that lies by omission are somehow exempt on their part. A lie is a lie, is a lie! or so says my mother. If someone states that "I only tell people what I think they need to hear", doesn't that suggest that omission of key facts in any form is not telling the entire truth. With that, is it a lie tell someone a major part of the truth, but leave out small facts - or vice versa - that give the truth substance? Is there any justification for it?