First of all, I have to say that I absolutely love this game. The characters, story, and art are all wonderful. I tend to like to play games like this by focusing on one main love interest, then playing again to look at another. It's just a personal preference. Playthroughs with "I got serious with the mother, the daughter, the other daughter, the daughter's best friend, the sexy neighbor, and the robot maid" take away from the immersion in the reality of the story for me.
I've noticed in this game that, depending upon the woman, it can be hard to get a high friendship without going for romance/lust as well, plus there are decision points that you can't explore without having a high enough relationship. This seems especially true with Monica.
Can anyone suggest a way to get past that (other than cheating)?