@Jakken_Dean wooooooah this is late. but erm, here's a bit about Ruin:
She tends to be very quiet and observant, looking out for information that could be useful/ be used to her advantage. She usually keeps a level head and is very intelligent, but she's also socially inept when it comes to normal and pleasant conversations. She's not used to being around nice people (tell me if you need the back story for this) and she tends to push people away and act cold (you pretty much hit the nail on the head for this one) since she doesn't know how to deal with friendly people. if she ever becomes friends with anyone, she would most likely question them on their sanity and ask if they were sure they wanted to be friends.
She's also not a fan of overly arrogant people, and she has a knack at dealing with short-tempered people. and good at making comebacks at jerks. she has no problem talking to these kinds of people as she knows that she can just let her sharp tongue do the work, without worrying about hurting their feeling. Karma and all, y'know.
and damn thats long. if you need to know anything else, just pm me and I'll reply as soon as I can. good luck with the story and I hope you have fun plotting the characters' demise!