So you can technically get all the girls at the same time with the exception of the police lady and Kylie
As for how to get Emma u need to basically get her done FIRST before any other girls if u go on a date with any other girl it would be very long for me to explain how to fix it so short of starting a new save yes she is a lost cause but that's ok though bc you can't do much with her and literally can only get a blowjob from her