CHELSEA Clinton may end up being one of the best-paid college graduates ever. The McKinsey and Boston consulting firms are both vying for the Oxford scholar, and one source said, "McKinsey has upped the ante and offered her close to $100,000 a year." It beats the $60,000 PAGE SIX reported she was offered last month. Clinton's area of specialty? Health care, of course. "Chelsea wants to take over where her mother left off," our spy snickered, referring to Hillary Clinton's embarrassingly failed attempt in 1993 to establish a federal health care service.