You for Queen, Me for Country

When Emerald first passes information to the tall, blonde spy with sparkling blue eyes she thought it was a one and done thing. She gave him the information, she left and never saw him again, she's American, he's British that should be the end of it.
Then her handler informs her that MI6 and the CIA will be working together in a joint operation, and she will be getting a British partner.
She is partnered with James Bond, a man as pretentious as he is handsome, over time they become friends. And together they face what they slowly come to realize it a great threat to both their beloved countries.