Special Agent Olivia Sparling is an agent with the Federal Bureau of Investigation who is partnered with Lance Sweets. Originally antagonistic, she develops a respects for Sweets' abilities and processes, and, despite accidentally shooting him, is clearly attracted. They went out on a couple of dates soon after her first appearance, and slept together once, but the timing or chemistry wasn't quite there and they drifted apart.
In The Gunk in the Garage, Olivia Sparling is a new FBI agent who is chosen practically at random by Caroline Julian to assist Sweets in an investigation while Booth is helping Caroline justify the department's budget. Although she initially has a low opinion of Sweets' abilities as an agent, after his knowledge allows them to identify their victim based on his assessment of the victim's previously-unknown twin brother, Sparling comes to respect his insight.
Following this meeting, Sparling and Sweets went out twice and slept together once, but it proved to be fundamentally unsatisfying as they decided not to continue the relationship.
In The Shot in the Dark, Sparling assists the team in investigating a shooting in the Jeffersonian that results in the death of a security guard and Doctor Temperance Brennan being hospitalized after being shot in the gut with a blood bullet. During this investigation, Sparling investigates the apartment of a recently-discovered victim with Sweets, determining that the victim was making far more money than he could have ever legitimately earned, and also helps keep Booth focused on the case when he nearly attacks the man who shot Brennan.