Relationships 2: mutual use

This is a situation I have found myself in before. I thought at the time it was not really a good place to be, for me. But is this an OK sort of relationship? I am concerned that by writing all this stuff I am going to sound all preachy and like: “Here I am in my happy relationship and I am try to say that everyone else should be in the same place”. I am not trying to say this. I am simple concerned for my friend and am trying to understand her position. I want to support her, but at the same time I have in the passed been accused of agreeing with everyone on everything, so I am trying to workout what I think of her situation. A difficult tight rope to walk. Still thinking........