I really liked the 5 dysfunctions of a Team (Patrick Lencioni). It's written for business, but I immediately also saw the correlation to personal life.
I would highly suggests the Marcus Buckingham (from the GALLUP organization) duo....... FIRST, Break all the Rules and then NOW, Discover your Strengths. The 2nd book - NOW, Discover your Strengths has a quiz at the end that will provide her top 10 innate strengths and how to use them to her advantage.
I also love the books that are smaller and written for a quick read:
FISH (Stephen Lundin)
Who Moved My Cheese (Spencer Johnson)
Gung Ho, Raving Fans and Whale Done (all by Ken Blanchard)