Hey, Zoya!
Welcome! I loved reading your app. You write really well, and I like the way you've designed Alex. She's a good, strong character, and I always like those who are strong from the outset.
That being said, though, for me, I don't see that Alex carries the mind and heart of a Gryffindor. She carries more the heart of a Slytherin. Both houses carry the dominant personality types, but what I see in a Gryffindor is the overwhelming drive to try to protect the ones they love and the overall society through unyielding devotion and self sacrifice. That's not to say that a Gryffindor can't have much too much confidence. They certainly can.
What I see in a Slytherin is a strong family tie or expectation of a tie due to position or tradition, with an undercurrent, often times, of being motivated for one's own gain.
When I look at Alex, I'm specifically looking for what drives her. Is it the love of others and her desire to protect? Not sure I"m seeing that. I'm seeing that her desire is more driven to protect herself and her own needs, and at sometimes, showing a disregard for the thoughts and feelings of others. That sort of focus, for me, rings far more true of a Slytherin heart.
If I am misunderstanding, perhaps you'd like to clarify for me?
Thanks,
k.