Jemma
Everything is a move to garner trust. When undercover, you are no longer yourself, you're playing a role. Sometimes you have to do things the real you would never do. You have to make the marks trust you. Believe you. You bury who you are inside and don't let them out until the mission is over. The person the team sees may share some traits and similarities, because you can't make people trust you if you're not genuine. A little bit of truth sprinkled inside the lies makes the lies ring true.
And it also means you can manipulate people even if your cover is blown. Was she really that bad? Maybe there's some good inside of her.