I was going to make a similar comment to what morethan1 made. Relationships do affect the people who are in the relationship, which in turn, indirectly affects the other relationships. But that is true with everything in life. My job can change my mood, as well as the weather, today's traffic, the movie I just watched, the news on the radio, and so on and so on. What affects me, can affect the people who interact with me. So theoretically, we are all interconnected in some minute way. *grin*
But on a the large scale, I'd say that each relationship is an independent entity.
Scheduling, on the other hand, is often dependent on other activities happening in your life. When the girlfriend needs to reschedule a date, I have to verify that nothing else is happening on that date, and if it is, whether it can be moved. This can get interesting when your V relationship is part of longer chain of connected Vs (I call them polymers)