I don't think I really commented on the last chapter; everyone covered what I wanted to say. You have very smooth, flowing prose, which I enjoy. The only hiccups occur in your POV thoughts/reflections, which sometimes feel a little clumsy. They don't just flow quite as well as the rest of the writing. But really, its all enjoyable to read. the bit where she realized she enjoyed kissing him was well done.
Almost instantly I liked her character more than the boys. I'm not quite sure why, but if I had to guess I think it's because she's so much more capable than he is. Miki, though still enjoyable to read, wasn't in a position of power – the entire time he's forced to be at everyone else's beck and call. Even though Sancha is working under several people, you see that she's quite good at it – even if her tutors are strict – and she has strong drive and ambition. These all make her very likable. Miki, though, just seemed like a goofball chafing under his teachers because he's young and wants to go sailing. At two chapters, of course, it's bad to make these kind of judgements, but readers will too so you should make sure he's just as likeable as she is.
I also like the small bits of the world you've shown us, and I'd like to know more about it. It's clearly a secondary world fiction, but I have to ask if it has any magic. Right now it reads like a K.J. parker novel, not in voice but certainly in setting – that is, it doesn't have magic but societies might have evolved a little different than ours so there's still room to experiment in worldbuilding. That's perfectly fine, and I've always enjoyed Parker's novels. But if you DO have magic – and I'm only saying this because it's secondary world fiction – than we should have seen it by now. Even if it's a very small magic, you should let us know it's there through conversations or rumors or legends, so readers know what they're getting into.