how many stats you need depends solely on how complicated (systematic) behavior you want to model. if you want to show both romantic AND abusive routes existing simultaneously, there has to be two stats to make possible situations like the girl hating you but still having sex. or loving you but not being open to degrading sex. it all depends on how complex/conflicted behavior you want to model. conflicting behavior can never be modeled with the same stat.
but if all your 'lust' behavior is also consensual/benign in nature like the 'love' behavior, you can cover it with the one 'love' stat.