I feel like Titania is a wonderfully made character. She breaks apart the stereotype that all hero's and good guy must be aligned as to pure light rather than neutral or dark alignment (in the RPG sense of alignment). I personally have found that grey characters are the most interesting because they operate according to their own terms and goals rather than following some other ideology of the masses. This leads to more questions about why the character reached their current development rather than accepting it as they're good so they're good.
While I find her interesting as a character, if she were a real person I don't believe that I would have the same belief. As stated in the starting post, she's manipulative, probably sociopathic, and apathetic to basically everyone. These aren't good personality traits, and yes killing people is not acceptable either. Yet, in her own world, all of these make her a stronger CHARACTER vs a stronger PERSON. Moreover, the people she kills are part of an organization that will stop at nothing to achieve their goals; she makes them nothing to stop their goals. I wouldn't approve of her actions in reality, but then again, why hold all heroes to a perfect standard? There's really not right or wrong besides what we decide together and for ourselves, and even if we have perfect standards we're aiming for, not everyone can be the perfect hero. You are who you are, and in Titania's case, she's interesting from observation but in interaction she'd be a mess to deal with (unless you're Amaria :3).