Played a few times through and decided to play 100% monogamous path but no matter what I try I can not avoid date with Amy at underground and back at hotel. I prevent Albert going to Birthday, turn her down at every turn yet I always end up in that room. Tried downloading walkthrough and avoided every listed trigger. Is only way to avoid Amy to actually miss movie date with Melody so you can actually have lunch date with Amy and actually turn her down when she actually asks directly? It would be annoying to be unable to max relationship with Melody just to be monogamous with Melody.
Been a manwhore so much easier and fun.
EDIT ok after several more efforts the trigger is simply the expensive perfume or lunch, having Arnold at birthday or not is irrelevant and the lunch is only secondary trigger, Still lose 2 points from Melody but I can live with that.