Congrats on your first game and game jam, this is an amazing first creation! The art is super cute. I can't wait to see more characters in the future. It was interesting to see how the player, as the writer, would be changing the dialogue to be in letter form, e.g. changing pronouns and such to make it match more or leaving out the incidentals. Really subtle detail, but really writes home what this game is about. 😅
I ended up submitting a blank letter as I scrolled past their dialogue and they left. I don't think you need the extra click/selection window, as the player is already scrolling and reading through the dialogue as their selection to add to the letter. Just have that be it and have fold be the dismiss the character button, so then the player can't get locked into a sad state where they weren't done. (And as another mentioned the send button was a bit fiddly at activating, if its time locked for a second then it should be grayed out during that period or appear after.) It could be fun to stamp/seal the letter closed.
I'm glad there were ratings at the end, though maybe shifts could occur a bit more frequently to get a progress report earlier to know you're on the right track. And as others have said, a wider variety of dialogue and personality to each character will go a long way.
I hope you decide to do a v2 post-jam!