We know that Yukiho has redeeming qualities and we know that the story has a happy ending (in at least the immediate future) because the structure of the story is a light-hearted RomCom, not an angsty drama. The mangaka didn't telegraph that love confession in front of the fountain for nothing.
Aside from which, the omake makes it even more clear. They've been dating for a month (wouldn't happen if Yukiho didn't have redeeming qualities) AND Yukiho confesses love to someone for the first time. She's a good egg even if we don't see it on the page.