Ok there are a couple of ways
When asked about relationship with Eric the first time you meet say you are looking for someone else. Be supportive of Eve or suggest Dave could cheat on her. Doesn't do much but makes her consider her relationship. At party for Eric leaving kiss her to avoid dancing with gang members. This sets up lesbian route.
The key to get into relationship with Eve is to have her or Dave break it off. Also Ash needs to break up or have open relationship with Eric at first oppurtunity.
1. You can continue to flirt and kiss with Eve at every opportunity until eventually she will confess to you and you can make it formal. This is for the good Eve path. Also better for this path for her to not have interaction with Jack, so at the first time at gym have Jack focus on you.
2. You can introduce Eve to Jack at gym which gets her invited to Jess party. From there Eve develops a bad girl persona. Avoid her when she offers chance to spend time with Wilson but don't turn down her friendship. You will get option to advice Dave to dump her and this leads to chance to romance her. You get a naughty/inqusitive Eve here.
3. Follow path 2 but join Eve in having fun with Wilson and both of you end up joining the gang. (optional for you). This is hardcore bad Eve but be warned this is not a pure lesbian path.