Sue White is the hospital's staff liaison officer, describing her job position as "to soothe, to bathe, to listen to the worker's woes". She often is seen to have quite eccentric behavior, such as dressing as a squirrel and refusing to speak any language other than crow.
She is probably bisexual. As well as having had a (short) relationship with Guy and been in love with Mac she has also shown an interest in Caroline. She has the most interaction with all the other characters, with all of them going to see her at one time or another, however unhelpful she has proven herself to be. She enjoys painting and listening to funk music.
The feeling between Caroline and Sue is mostly negative, with a vague sexual undertone, as Caroline and Sue have kissed multiple times. The main source of conflict between them seems to be their mutual love of Mac, driving Sue to even attempt to kill Caroline many times. However, they seem to make up, as Sue is one of Caroline's bridesmaids.
Guy and Sue openly hate each other, probably stemming from them sleeping together, which presumably included a strap-on and S&M. When Sue obtained a video tape of Guy and Joanna having sex from Martin, she attempts to blackmail Guy into breaking up Mac and Caroline, which ultimately fails as Mac reclaims the tape.
Sue is completely in love with and obsessed with Mac, citing his 'lion's mane' of hair. She attempted many times to seduce Mac, without success. When Mac was in a coma, she conducted a wedding ceremony, and stole some of his semen to make herself pregnant. She eventually gave birth to a lion which she named Simba. At Mac and Caroline's wedding, Sue seemed to have taken Mac's advice to find someone who would love her as she is with Jeremy, who she claims has a big penis. This could be the reasoning behind her making up with Caroline.
Similar to Mac and Guy, the relationship between Joanna and Sue is one of a constant battle for superiority, both in status and attractiveness. This particularly comes forwards when the film crew arrive at the hospital, as they both try to appear in charge. When Sue finds the video tape of Guy and Joanna, she uses it to blackmail Joanna into doing lots of things, such as making Sue fly.
Unlike most staff (apart from Mac) Sue seems to get on surprisingly well with Martin. She tries to help him with finding clothes for Caroline's housewarming party, even going to the lengths of going clothes shopping with him. He also trusts Sue enough to tell her about the video tape of Guy and Joanna, despite death threats from Guy.
Sue hates Holly, as she is competition for Mac's affection. Sue is the one who discovers that Mackenzie isn't Mac's son by finding some incriminating evidence that Holly keeps in her locker for some reason. This gets Holly kicked out.