The Fixer by Claudia Carroll

Meet Meg Monroe, the fixer. If you want to get rid of someone you call Meg. (No, not like that - this would be a very different book!)
Using her brilliant intuition, people reading skills and with masterful manipulation Meg befriends her mark and tells them what they want to hear, using it to convince them to see the error of their ways. She's never once found a case she can't handle - affairs, clingy former-friends, useless employees and exes that can't take the hint.