A lot of times when you obsess about something in someone else its projecting due to your own insecurity. Maybe you are insecure about your own attractiveness so that's why you focus on others. Does this have anything to do with how you think others view you? Like if you date an ugly woman they will think less of you? I agree that you should talk to a therapist about this. Whenever girls focus only on beautiful girls it tends to be because they don't really love or accept themselves.