Sandy really likes talking to belinda. every time she speaks with her, sandy feels calmer and less anxious. sandy is using her interactions with belinda to fulfill her

Sandy is using her interactions with Belinda to fulfill her "physical needs".

Needs are vital to human functioning. The idea of human needs comes from our biological nature, a nature that can be comprehensively seen in both mental and physical terms.  

Once the physical survival and security needs are being regularly fulfilled, an issue for adoration, friendship and having a place start with develop. This result from the way that individuals are amiable and require associations with others.

if interdependence implies a two-way dependence, and if each partner is equally dependent on the other for success, then there is an equal commitment to the making the partnership successful. the advantage is sustainability of the relationship, the disadvantage is that decisions are "democratic" and therefore may take longer to reach and more likely to be a compromise (which is not always the best solution). as the interdependence moves away from equality, the decisions become more influenced by the more independent partner. in the extreme the relationship becomes more dictatorial and more like "master-slave". generally the relationship has less commitment in both directions and is more likely to be temporary.

if one generalizes (and one shouldn't), equity partnerships, which is probably what is implied by interdependence, can be slow to progress or change but durable. the extreme alternative, independent-dependent partnerships tend to be efficient but more fragile.

hope this but you will have to site your own evidence. : )

well considering i can't see the graph, it's probably prices