Andrea complains of being lonely. She admits that she thinks other people are relatively unfriendly and concerned only about themselves. Several times, she has made the statement that the “world is full of people who wouldn’t hesitate to step on their best friend just to get ahead.” Andrea is probably lonely because of her

Andrea has clearly adopted a position of distrust and reluctance over the behavior of human beings. This state of wanting to avoid others has made her voluntarily adopt a state of isolation.

One can sense distrust in her argument when she mentions that people wouldn't t hesitate to betray their friends in order to get ahead. Regarding reluctance, she mentions that people are only concerned about themselves so that probably leads her to not open up and tell her problems to nobody.

It is a natural reaction to react with distrust towards others who don't grant it, so that makes people in Andrea's environment to also want to avoid her due to her attitude.

Andrea is probably lonely because of her trust issues, when she states that the world is full of people who would not hesitate to step on their best friend just to get ahead, she's demonstrating severe and generalized difficulty to trust anyone. This situation might stop her from developing new relations.