To Mara, there was nothing worse than living a life that was never fully realized. After all, such a life was an empty one, and she didn't like that. Life was something to take part in, not to watch go by. But she did understand where Galen was coming from. He'd been raised in an atmosphere where he was taught to be a killer and nothing more. He hadn't been taught to care about others and respect life and to enjoy it.
Mara listened as he voiced his thoughts. It was enlightening to her as she was able to see where Galen was mentally speaking. She could read his Force presence all she wanted, but that wouldn't give her access to the thoughts that were going through his mind. "Specifics of what kind of man you want to be will come as you move forward. For now, it is enough to want to be a better man than what Vader was forging you to become." The sentiment of killing Jedi, however, was one Mara could relate to. Well, sort of. "You are not the only one who killed Jedi. I have their blood on my hands. I have the blood of Force users of all sorts on my hands. I understand how it may feel wrong, but I rose to bear the title. I worked for it and earned it. But getting past that mentality of having killed them is a difficult one. That is something you need to accept and make your peace with because the man that killed those Jedi was a Sith apprentice. You are no longer a Sith apprentice here." Mara was hoping that showing Galen that it was all completely his own choice would help. She knew how hard it was to suddenly realize you had the ability to make choices for yourself and not because your master told you what to do.
At the confession that part of him wanted to be Gaia's champion, Mara looked at him. She was still wary of the Roman woman, so she wasn't completely sure if this would be a healthy thing for either Galen or Gaia, but she decided to be encouraging for the meantime because if Gaia helped Galen to feel? That was one step further away from the Dark side.
"If that is what you want, then you should do it." But she would still keep a close eye on this, and if it started going somewhere she didn't like, then she'd intervene. But until then, Galen needed to make his own choices and she wasn't about to force him into a choice, one way or the other.