Susan's parents, Cookie and Henry, are shown to be flighty (her father is jokingly referred to as a test pilot for Barcalounger) and difficult to talk to.

Her older sister, Chloe, is the source of most of her distress, with a seemingly never-ending series of problems with alcohol, drugs, men, and money.

Already overstressed, Susan clashes numerous times with the new Chief Resident, Kerry Weaver, forcing Mark Greene to step in between them.

Susan grows extremely attached to the baby, but she gets a surprise when a reformed Chloe reappears later in the season and tries to reclaim "Little Susie".

Desperate to keep the baby, Susan attempts to fight Chloe for custody, but she is forced to reconsider when the judge warns her that she would lose.

Susan begrudgingly reaches an agreement with her sister, and after regaining custody of "Little Susie", Chloe moves her family to Phoenix, Arizona to start a new life.

Although many ER staff members hoped for Susan to attain the title, she declines the position, expressing to Mark that there is more to life than work.

Setting up Stringfield's departure from the series in season 3, the beginnings of a romance develops between Susan and Mark, or more to the point, they are shown to have problems identifying their current relationship as friendship.

Initially more upfront one about the situation, Susan invites Mark to join her on holiday in Maui, Hawaii, but is embarrassed when he appears hesitant, causing her to later retract the offer, feeling she overstepped a boundary.

Shortly after, Mark witnesses Susan in numerous secret talks with the ER's chief of emergency medicine, David Morgenstern, and concludes that they are seeing each other.

During a hectic last day for Susan at County's ER, Mark struggles with her imminent departure, but still finds himself afraid to admit his true feelings for her.

The hospital staff arrange a going away party for Susan, but it is canceled due to an influx of critical patients from a car accident.

She meets Mark for coffee and reveals that Chloe has moved on to another city, and she has decided that she can't follow her sister's family around forever.

Her problems with Chloe resurface when her niece Susie goes missing in New York after leaving a distressing voicemail message on her aunt's phone.

Throughout the season, Susan faces one of her most difficult story lines, as her best friend Mark Greene reveals to her that his brain tumor has returned.

After her best friend's death, Susan warmed up to other friendships in the ER with Abby Lockhart and Elizabeth Corday, and was able to work better with her old colleague Kerry Weaver.

During season 9, Susan meets a flight nurse named Chuck Martin (played by Donal Logue) on a plane to Las Vegas.

When the only tenure spot goes to her friend John Carter, due to her lack of grant funding, she clearly gives up on County and this leads to her final exit from the series at the beginning of season 12 in the episode "Canon City".

In contrast to the major attention given to Stringfield's departure from the series back in Season 3's November sweeps period, her second goodbye came in the S12 premiere, an episode which she had very little to do in, and gave no indication she was leaving for good (in fact, the show had Dr. Kerry Weaver tell the staff several episodes later about how Susan wouldn't return after accepting a tenure track position at a hospital in Iowa City, Iowa).

She eventually returns to the ER for the last time in the series with Rachel Greene and Carter, where she visits and jokes with the staff, much to the annoyance of Dr. Banfield who interrupts the talk by asking Susan who she is.

"[8] According to Entertainment Weekly, people called Stringfield "nuts" for leaving "the hottest show on TV for some investment banker in New York.