Virtually Series (1-2) by Gennita Low

Virtually His (Virtually #1)
Chosen to be the ultimate secret operative, Helen Roston has become the most dangerous woman in the world. Two years of training and she's now ready for the final phase-- a risky combination of virtual reality and a mind-altering serum. When her mysterious and faceless "trainer" syncs his mind to hers using the program, she's amazed at her sizzling response to his virtual touch. But Helen likes to be in control. She's "not" going to beg for more.

Helen's final test is a challenging mission, picked by the other government agencies whose candidates lost out to her.

To succeed, she has to put herself completely in the hands of her trainer, a man she's not sure she can trust. But all of COS Command are counting on her. She cannot fail.

Virtually Hers (Virtually #2)
He can't get her out of his head...literally. Virtually, Book 2 In Helen Hell Roston's elite black ops world, failure isn't listed as an option in the rule book. As the leading guinea pig in a dangerous combination of virtual reality training and a mind-altering serum, though, every day offers a thousand ways to blow it. And the very real sexual chemistry that sizzles between Hell and her trainer is messing with her head even more. COS Commando Jed McNeil is an expert in mind manipulation games. He's been chosen to be Hell's monitor and anchor in the Super Soldier Spy program. Trained to compartmentalize his needs and feelings in an assignment, he's unprepared by how much Hell affects him. When the experimental serum gives Helen incapacitating headaches, her pain throws Jed into protect-at-all-costs mode. A position the fiercely independent Hell would rather die than be in. But with a rogue CIA faction out to sabotage the program, Hell has no choice-even if it makes her head explode. It's trust Jed, or die. Book 1 of this series was published by the Mira imprint of Harlequin. Warning: Contains scenes of voyeuristic hanky panky, bad guys that feed off mind-blowing sexual energy, a heroine who knows how to get her kick-ass on, and a hero who gives as good as he gets.