I think there's a way to help someone who is honestly asking for personal help (why don't I have friends, why am I always excluded from the dinner parties, why do I never have a second date, why do my kids disrespect me, etc). You've got to discern whether the person is just complaining ("i have no friends") or genuinely asking for input.
First, it's important that you have a good relationship with the person.
Second, it's important to stick to the subject. Don't overwhelm by saying, well, you curse and you rant and there was that time that you lied and you're always late and sometimes you're rude to servers in restaurants, and on and on. These all may be true, but if she's asking why she isn't invited to your weekly happy hour get-togethers, stick to that. "Josephine, when we've invited you in the past, you were so loud in criticizing the service at every opportunity, even when the poor guy was bumped into by the elderly woman who fell, causing him to drop what he was carrying, it's just not pleasant. And it happens every single time. We'd love to include you, if you were more gracious towards the hard-working staff, more discrete, and didn't monopolize the conversation by griping about the service".
And third, don't try to say "no one likes..." or "everybody hates....". Be kind. "Well, Josephine, to answer your question, sometimes you have a tendency to share information that isn't yours to share. Maybe you can ask yourself, before saying something about someone's marriage, job, baby, or other situation, if this information is necessary, kind and truthful and helpful. It's difficult to socialize with you, not knowing what inappropriate information you're going to put forth. I'd love to help you."