Stay Eva's friend (don't tell her to fuck off or 'don't you dare to judge me') and keep her out of Jack's clutches. At Eric's farewell party pretend to be a lesbian and kiss Eva. Later tell her you liked kissing her. In the gym's shower ask her if she wants to do it again. Soon after you will have an opportunity to have sex with her for the first time ('There is nothing wrong with it'). After that use every occasion to enjoy time together. You will need at least 15 Good points to become Eva's girlfriend.