Jack isn’t one of the original members of Shepard’s team, but from the moment she appeared on the series, she definitely leaves a lasting impression. She won’t join until after Mass Effect 1. So this is the way to be romantic with Jack in “Mass Effect 2” and “Mass Effect 3.”
How to Romance Jack in Mass Effect 2
First, you need to be a male Shepard to romance Jack. After recruiting her by completing “Dossier: The Convict”, she will become only the lower level of the Normandy alone. After several conversations, you will have a chance to one-night stand type fling with her.
She thinks you’re just talking to her just for sex, and she made it very clear. Make sure to avoid using the “Yes, I want you” option to reject her proposal, because if you don’t, she will never open her heart to you in the next game and romance will be impossible.
After completing the “Jack: Subject Zero” loyalty mission, you can finally start to open up your romance plot story. After a few short conversations make sure to choose the option that don’t set her off, finally you will have the opportunity to choose “I’m interested”, which will start a relationship.
Once you have completed Jack and Miranda’s loyalty mission (in either orders), they will enter into an argument. At that point, you have to choose who to be with or, if you have enough Paragon or Renegade points, you can solve the problem yourself. If you don’t, side with Jack. Once the discussion is over, Miranda’s loyalty can be restored by having another conversation with another Paragon / Renegade.
After expressing your interest, you can choose to say “I want to talk about us” so that you can learn more about Jack. Make sure to assure her that you will be with her. In the next dialogue, Jack will open up more, and when she does, give her a moment to do so. Rushing her, interrupting her, or showing no interest will lead to the end of the relationship.
Finally, Jack will enter your room before the suicide mission. Choose “I’m glad you’re here” to lock in the romantic plot of “Mass Effect 3”. Make sure she survives the mission and can see her again in the sequel.