Donna is an excellent networker and was "tied-in" to the gossip and under-belly happenings of Pearson Hardman. Her network is extensive and runs through most of New York City. As a result, Donna is regarded somewhat warily by associates and partners alike. However, she is an excellent confidante and a great people person, which allows her to maintain relationships with people that Harvey cannot. She is social, fun, witty, and charming, and people enjoy interacting with her.
Harvey Specter is Donna's longtime boss and close friend. Both trust each other implicitly. They first met at the District Attorney's office, where Harvey was Assistant District Attorney (ADA) and she was his secretary; they have been a team ever since. After working for two years at the DA's office, Harvey took Donna with him to Pearson Hardman.
The two are extremely close. Harvey loves her and trusts her absolutely. He relies upon her and views her as essential to his being. As he told Jessica in "All In," Donna is irreplaceable. Donna, in turn, adores Harvey and is incredibly loyal to him, to the point where she would take a bullet for him. Both tend to view each other as two halves to the same whole, and Donna has put Harvey above all other relationships more than once. They take great pleasure in each other's company and enjoy their jokes and verbal sparring. (They have a pre-trial ritual involving a can opener and thumbtacks.) Over the years, they have developed an ease of comfort found only between best friends, and are very good at reading the other. No one knows Harvey better than Donna, and although Harvey generally tends to keep his feelings close to the chest, he is more open and vulnerable with her than he is with anyone else. She is privy to most of the details of his private life--she knows about Harvey's mother and brother, and is fond of Harvey's father. (She is also the one who informed Harvey of his father's death.) Donna is also one of the few people whose opinion Harvey values, and he listens carefully to anything she tells him, even if he does not always acknowledge it at the time. When upset, Harvey sometimes falls back upon establishing the boss-employee boundary--a boundary Donna is smart enough to know when to ignore, recognizing it for the emotionally distancing tactic that it is. She is likely the only person capable of keeping his reckless tendencies in check. Harvey, meanwhile, is equally good at reading Donna, and although Harvey is not essential for the mechanics of Donna's life, she relies heavily upon his unswerving loyalty, devotion, and emotional support. Despite being protective of his privacy, Harvey has let Donna's parents stay at his condo before (after she cried fake tears--a fact he only finds out later), and Donna has the spare key to his condo.
Donna is a gold mine of information for Harvey and listens in to all his conversations in his office (something Harvey does not discourage, since he leaves his intercom on for her). She is excellent at anticipating his needs, and takes great pride in being able to provide Harvey with what he needs without him asking for it. She views her job as to protect and take care of him, and will go to any lengths to do so. This was first proven in "Rules of the Game", where she gives Jessica incriminating evidence against Cameron Dennis after Dennis threatens Harvey, and again in "Break Point", when she shreds an incriminating memo that she fears will implicate him in a lawsuit.
The events in "Break Point" emotionally strain and confuse their relationship. Travis Tanner resurrects an old lawsuit against Harvey, accusing him of burying evidence and committing fraud. Harvey denies the accusations, stating that he never received the memorandum supposedly in his possession. Donna, however, finds the document in the file room with her date stamp on it. Afraid of the implications against Harvey and seeking to protect him, she hides the truth from him. Harvey nearly commits perjury as a result, and it is only Mike's quick actions that prevent him from doing so. After Mike informs Harvey that Donna found the document, Harvey storms into the ladies' room to confront her. A bitter argument ensues, during which Donna accuses Harvey of keeping things from her and she tells him that she shredded the memo. Feeling furious and betrayed, Harvey tells Donna: "I'm not going to fire you, Donna--I might KILL you--but I'm not going to fire you."
This makes their relationship extremely tense. Both Harvey and Donna are used to being perfectly in sync with each other, and for the first time in a long time, they are out of step. It frightens and confuses Donna that she could have misread the situation (and Harvey) so badly. Harvey, on the other hand, is swamped by his feelings of fury, hurt, and betrayal, and can see little else. He is hurt and upset that she did not trust him enough to come to him with her problems, and a part of him is frightened that she would go to such lengths to protect him. He is afraid that this is something he cannot fix. These are two people who typically know what to do in any situation, and for the first time, both are at a loss. These feelings are further compounded when Jessica fires Donna--Donna feels hurt and betrayed that Harvey didn't fight for her the same way he fought for Mike, while Harvey is uncertain as to how to fight for Donna. His own personal credo of "tough, but fair" creates a conflict within him: on the one hand, he loves Donna and views her as essential to his being; on the other hand, her actions make her termination more than justified. Harvey is at a loss as to what to do, and he is lost without Donna.
While Donna manages to go on with her now Harvey-free life in "All In" and "Sucker Punch", Harvey is incapable of moving on without her. His grief over her departure is so strong that he becomes incredibly reckless, and no one can hold him in check--not even Mike or Jessica. It is only at the end of the episode "Rewind" that Harvey informs Jessica in no uncertain terms that he's bringing Donna back, and it is only in "Asterisk" that the rift between Donna and Harvey is finally mended.
While it is implied late in the first season and throughout the second season that Donna's feelings for Harvey may not be platonic, she informs him in "Asterisk" that she "loves him like a brother or a cousin" and that she is not in love with him. It is unclear if we can take Donna at her word, however, since she is also an excellent actress and has fooled Harvey before.
During the episode "The Other Time" which is referenced in "Asterisk" it becomes clear during flashbacks that Harvey once tried to pursue Donna, but due to her policy of not mixing work with pleasure, she resisted his advances. However when both Donna and Harvey quit the DA's office Harvey visits Donna and she was already waiting for him with a can of whipped cream. Harvey steps into her apartment and she closes the door and he leaned over to kiss her. Although it's not seen, producer Aaron Korsh confimed in an interview that they slept together during this flashback. Afterwards when Harvey gets a new job at then Pearson Hardman, and he asks Donna to work with him to which she agrees on two conditions: a large signing bonus and never to speak of them sleeping together again. The episode also shows where their loose banter and can opener ritual originate from.
At the end of Season 4, after working for nearly 13 years together, Donna quits being Harvey's assistant and is now working for Louis. She decided this because her relationship with Harvey is not working for her. Louis also said to her in a conversation that Harvey is unaware how lucky he is to have Donna. Also Norma, Louis's own assistant, passed away. Before leaving she tells Harvey that she loves him.
After Mike Ross is arrested in the middle of season 5, Louis fires Donna so that she could become Harvey's secretary again and help him help Mike.
