Usually it's a person hungering for the love of that special person to lift them out of feeling bad. Their sense of self-worth skyrockets, and it gives them a boost. Even if something happened that wasn't a big deal for Clinton, imagine how big a deal it would be for her. I can understand why she would need to confide in someone. I could also imagine that the intense need for public secrecy could make her private disclosures even more involved and detailed, energized and charged, as a counterbalance.
Women place a much higher value on that bond than men do, generally.
It may have been a violation for Clinton to hit on an intern, but for a close confidant to record those conversations and hand them over to someone else, that's horrible. That's emotional rape. I tell them that to regain control of their behavioral decisions, it helps most to accept those impulses within yourself. If you want to make your problems with impulses worse, the best thing to do is fight them. And I tell them that if you're in a fight with your eroticism, you will lose.