It's not a perfect game, but it's a pretty damn good one. A lot of that I chalk up to the script, and the subtle revelations of personalities that occur as a result of specific speech opportunities needing to be functionally equivalent (e.g. revealing the same piece of information or prompting the same response from Squall), yet distinct enough such that who you choose to be in your party makes a difference to the player. I've selected a few below that I think I reveal Quistis's personality in contrast to the remaining team members.

ZELL: We fought you, too, knowing you were our Matron.
IRVINE: We fought, knowing you were our Matron.
SELPHIE: We fought you, even though we know you were our Matron...
QUISTIS: We fought, knowing very well that you were out Matron. That was the only choice we had left.

After the liberi fatali realize that Sorceress Edea is Matron Edea, who raised them all prior to their various adoptions, they continue to fight against her. Though it's later revealed that she wasn't in full control of her faculties, nonetheless they were, and when they finally speak to Edea as herself that choice has to be addressed. Interestingly, though there are slight dialogue differences, only Quistis provides a truly distinct response. They all acknowledge that they recognized her; only Quistis states that their choice was due to a lack of options. Strictly speaking, that's not true. At any point they could have laid down arms, perhaps attempted to approach her more diplomatically, or retrieved a defeated Seifer for interrogation before fleeing Edea. Of course, the game doesn't give you that option. That FFVIII frequently ponders the bounds of choice is interesting for a game, particularly in the ways that it references its game-ness. When Squall dreams that he is Laguna Loire, for example, he reports being unable to affect any of Laguna's choices, but the dream doesn't end until Squall and the player complete a series of helpless tasks. That's precisely the way it is when the player takes on Squall's role. You must become a SeeD. You must build a rapport with your team and Rinoa Heartilly. You must defeat Edea. You must defeat Ultimecia. Failing to do any of these things simply locks you in the same part of the game, at whatever your most recent save point was — it doesn't create a new situation.

What makes this tidbit interesting isn't simply what makes FFVIII interesting; Quistis doesn't see personal relationships as a mitigating factor in combating evil. No one else says anything about what trumped care for this woman, and technically, she doesn't address what made this choice the only choice. One could imagine, however, that since they had no reason to believe from recent actions that Edea was up to anything good, Quistis thought there was no reason to hesitate. Yes, I knew it was you. I also knew you were trying to take over the world. #sorryntosorry. In other words, it was Edea's actions that left no choice on Quistis's part. If I'm right about analysis elsewhere, where I attribute a particular emotional concern to Instructor Trepe, this is a counterexample. At the very least, it complicates the view that she puts friends first. You have to wonder about a woman who chose to be a mercenary and yet seems to prioritize moral concerns over personal concerns — did she think that Garden would save the world? Is this an inconsistency? Being a SeeD seems to mean that you have no choice about what your missions are, and so have no choice about what objectives you achieve and what consequences those bear. Meaning: morality ain't got not place there. I read it as an interesting lack of integration in her values. I think she puts moral concerns above caring for others, but caring for others is a kind of moral concern; in contrast, I see her involvement in SeeD as a push towards personal excellence sometimes, though not always, in conflict with the former.

ZELL: OHHH YEAHHH!!! We're in!
QUISTIS: Ready guys!?
SELPHIE: You betcha!
IRVINE: (For me and Selphie!)
QUISTIS (This is it! For the world!)
SELFIE: (For Balamb and Trabia!)
ZELL: (It's payback time!!)

During the conflict of the Gardens, where mobile Balamb and Galbadia Gardens smash into one another as their students launch a full-scale assault, certain team members can announce what they're fighting for. It's a constant source of charm to me that Irvine alludes frequently to his care for Selphie, which doesn't really go reciprocated except in her rage at his flirtatiousness in the closing video. She's too busy running festivals, building fansites, and singing train songs. Locomotives before brocomotives, you know? Anyway. Even as Irvine fights for a future for the two of them, Selphie is specifically fighting for the home she lost and the one she hopes to build, Zell fights to avenge the wrong doing that Galbadia Garden and Seifer have done, perhaps particularly their occupation of his home town of Balamb, and Quistis fights ... for the world, broadly. Again, this is an allusion to moral concern on her part, and it makes me wonder what our girl was doing as a shill for an international military body. It's also a place where one could wonder about what she wants and needs. Everyone else seems to have something specific they're thinking of. Irvine thinks of relationships, Selphie thinks of two different homes, Zell thinks of vengeance (which comes off as endearing rather than cut-throat, because this is hot-dog Zell we're talking about), and Quistis thinks of everyone else.

SELPHIE: Oh! Neato! A hole in the middle of nowhere.
IRVINE: That's weird! Is that a tunnel or something?
QUISTIS that? How can there be a hole in midair?
ZELL: WHOA! What the hell is that!? It's some kinda hole or tunnel...

Generally, when given equivalent conversation opportunities, both Zell and Selphie's come off as the most distinct. Zell is really taken aback by this hole in the sky when the team is looking for the city of Esthar and discovers an empty canyon with a tunnel midair. Selphie doesn't seem especially surprised, or if she is, she reacts to that surprise as pleasant: Cool, a hole! Both Irvine and Quistis seem a little more experienced here, although Quistis is the only one who seems to be thinking out loud about what the significance of this is. Much of her lines have this feature, of just a few nanoseconds of further assessment. Much earlier, when Squall is first piloting mobile Balamb Garden and the whole team has to effectively say WE'RE GOING TO CRASH, she's the one that says "Brace yourselves". It's a subtle difference, but it's just a smidgen ahead of everyone else, directing them to what possible actions this will require -- or perhaps it only seems that way, because so many of her reactions have concern for the team parceled in, and so often feature actions to be taken.

SELPHIE: (...Are we locked in? Squall will take care of the rest, right? I wonder if he'll organize the Garden Festival? Nah, can't count on Squall for that... Sigh... It's all over...)
RINOA: ...Squall, did you put me on this team because you hated me...
ZELL: I've always thought about when this day would come. Living a life full of battles... I guess you could say I was prepared. But when I think this is really it... Damn, it pisses me off
QUISTIS: It came quite quietly. I thought the end would have been more dramatic...
IRVINE: Squall...He didn't trust me. That's probably why he put me on this team...
SELPHIE: (...What are you all saying? ...Squall chose us because he believed in us. I'm sure of it! We can do it. That's what he thought when he made this team. Isn't that right, Squall?)

Should Quistis take part in the infiltration of Trabia Garden with Selphie, there is a moment when the whole party is certain they are about to die, as their exit is blocked by the husk of a defeated robot and they've just rigged the base to blow. Though there are other near-death moments in the game, this is the only one that both offers a moment for reflection and comment. Each character's contribution is interesting, but what I loved about the reveal for Quistis is that she has evidently never expected a lengthy life, or a quiet death -- all along, she's expected violence at the end. In some ways that goes against what you expect from our instructor. Isn't she the mature one? And yet, I think this tells us that she might have hoped for more glory than her dialogues with others reveal; or, perhaps more accurately, she's never hoped for peace.