I'm really trying to give Ryuko a pass on this one.

She's a teenage soldier who was out for revenge and got caught up in an intergalactic war. Why are you expecting a well-written justification? Reality doesn't come with well-written justifications. Realistic characters don't have the time to make well-written justifications of their actions, they barely have enough time to do the things that fans demand justifications for. I hate when viewers demand flawless logic out of temperamental characters who don't have the weeks to sit around and critique their own actions because they're too busy staying alive. Fans are like armchair generals, with the 20/20 hindsight that makes it easy for them to say "Why didn't you just do X? I would have done X, would've been way easier." Yeah, well, no, you wouldn't have done X, you wouldn't have had the time to think of doing X. Characters don't get the benefit of being able to watch their actions in the comfort of their own homes, being well-fed and fully rested. In their action-packed, plot-twisted world, it's do or die. There isn't the time to think of why you're doing something and only barely enough time to actually do it. It's the modern-day "Man in the Arena".