Nina went from a funny character to a rather annoying character after he got shot
Really I have to date her now? Why the hell would that not be optional? What a terrible decision.
..... interesting.... while I understand why you view her that way, I have to say that you have misinterpreted her character, but that makes sense considering most people don't know the many variety of ways other hide their true selves, deflect their emotions, etc.
but for the sake of explanation, she became an "annoying" character because she was scared. (in the most simplistic of terms) like when she was sad that the mc was leaving she pretended she didn't care and that she hated him to try and make it easier for the goodbye (which if you know anything about human emotions and how to properly deal with them this only makes things worse and not better).
hope that helps you understand the character a bit more, you don't have to like her to each their own, but don't shit on the dev because you don't like something, read around and it is easy to find that this is the only open path currently as it is still in development.
P.S. I really wanted to go complete savage but I decided to try and take a neutral approach, because I am such a benevolent man.