I see why you'd say that, but think about it a bit more logically. The scene you're talking about... doesn't make sense in the real world. Yes, he massaged her and touched her breasts, but he was talking about "jumping her" as if they aren't both virgins and he isn't a guy who is clueless about girls and the signs they are interested. Yes, he got turned on (and so did she), but it would be extremely out of character for either of them who are not outgoing or experienced to suddenly go from never having kissed to having sex. Especially considering Eve's personality, she isn't the kind of girl who would just have casual sex without being in a relationship.
Lexi on the other hand, has made out with him, given him oral more than once, received oral from him, and the two of them have already openly talked about having sex with each other. Their relationship is just significantly farther along, and as I said above "if this was the real world" they would clearly be the first two to have sex, so if it isn't her then it's a choice by the dev and isn't driven by the story or the relationships because based on those it couldn't be anyone other than Lexi (or as an "underdog" Saki who has at least did something mutually sexual with him).