I really enjoyed this! It's an effective demo: the player gets a good solid sample of gameplay, then uncovers something about the game world that makes them want to learn the whole story.
SPOILER WARNING below here (just in case anyone reading this hasn't played it yet!)
It took me a little while to understand how the "press suspicious statements" puzzle mechanic worked, since Gema's self-introduction has two lines marked with a ! and the player has the option to press her on each of them. It made me think there would be a one-to-one correlation of ! marks to suspicious statements, but then more ! marks showed up on lines in the "Ask about ___" branches and didn't add any new options to the list of statements to press her on. After getting that the marks are general indicators that something is suspicious, I realized that they essentially tell the player "here's some evidence you might want," which diminishes my enjoyment of the puzzles. The contradiction-finding puzzles in the Phoenix Wright games made the player really look through all the text to find something relevant, so identifying the right piece of information was really satisfying. I know a lot of people find that frustrating, though. Maybe consider having a hint setting that can be turned on to show the ! marks and turned off to hide them?
I liked that when I tried to call Gema on her lie about being a medical officer before I'd asked her about her family, I didn't have the option to point out that she didn't go to medical school, only to say that she looked too counter-culture to be a doctor. It wasn't my first playthrough, so I knew she was lying, but this playthrough's SAM didn't have a good reason to suspect that, just a very flimsy reason. (Gema's response to that option is great, by the way.) That made it feel like I couldn't just pick from the choices at random until I got the right one, something I'm ashamed to admit I did occasionally in Phoenix Wright. This isn't consistently the case, though: at the point where the player can guess Gema's occupation, the roboticist option appears even in a playthrough where Gema hasn't talked about her interest in robots.
Incidentally, I did like the lack of consistency between the sets of options. What I mean is that it would have been easy to always have there be a right choice and a wrong choice, as in "robots"/"software" and "not alien"/"not raised on Earth," but then there's the case of "not a doctor"/"not in space," where either option is viable if you have the evidence to back it up. This is a pretty short demo, but I got the feeling that being able to solve puzzles from multiple angles might feature more in the full game.
The one mystery element that felt awkward to me was that SAM always questions whether or not they're really in space. Gema's lines to the effect of "it sure is something to be on the S.S. Vision, in space, where we are" all have ! marks, and I was confused as to why until I got to the end of my first playthrough. SAM figured it out before I did; they even ask Gema about it with no player input, whereas in every other case, the player directs SAM's questions to Gema. It felt like the game prioritized getting the plot twist information across instead of letting me solve that mystery by myself. I can see how that would be more effective for a demo, though, since that information is the main hook for getting the player intrigued.
Gema is a great character! I already really like her and want to see more of her. The artist did a terrific job on her, and she has a distinct voice that comes through even in this relatively short scene. Something I also appreciate about her is that she has anxiety and ADD, as the player learns right off the bat, and that's not presented as inherently funny or tragic or otherwise weird. That feels like a low standard to set for writing characters with mental illness(es), but a lot of works don't manage that, especially video games, so it's a pleasant surprise.
I'd be glad to point out spelling, grammar, and general language flow issues if you want (I apologize for bringing it up if not), but otherwise, that's all. Sorry this post is grotesquely long. Thank you for sharing your demo!