(Fan created content. Distinct from hoaxes and parodies)
"Sexy Blue Striped Shirt Girl", also known by the acronym SBSSG (and further known as Sarah Stripes by listeners of the LOST: Down the Hatch podcast), is the nickname, coined by fans, given to the survivor depicted by Faith Fay who is a middle-section survivor of Flight 815. The character has developed a minor cult following in various fan forums. The nickname comes from a blue striped shirt that she wears in the airport scenes and early beach scenes. The character's final appearance was in "Fire + Water", because Faith Fay then moved to California and ended work on Lost. However, she appeared in a memory when Jin and Sun woke up in "The End".
Faith Fay, the actress who portrays Sexy Blue Striped Shirt Girl, has done a Lostpedia interview describing her character's backstory. In the interview, Faith states that she would have been willing to return to Lost if the producers had wanted her back.
Before the crash
The Sexy Blue Striped Shirt Girl traveled to Sydney Airport to board Oceanic Flight 815. At the airport she waited in the check-in line, when Shannon was lying on the bench and later passed behind Sun, Jin, and Jack while they were at the check-in counter. ("White Rabbit") ("House of the Rising Sun")
SBSSG at Sydney Airport
She was also sitting next to Walt when Michael left to make a phone call. She then passed by Hurley when he was rushing to the security check-in, during this she had her arms around an unknown man. Soon after she boarded Oceanic 815. ("Exodus, Part 1") ("Exodus, Part 2")
On the Island
Days 1-44 (Season 1)
The Sexy Blue Striped Shirt Girl appeared during the initial aftermath of the crash and helped other injured survivors. At night while recovering, she heard the roars of what the survivors have come to name “The Monster” in the jungle.
The next day she watched a fight between Sayid and Sawyer. After the group began to panic about their supplies, Sayid made a speech about forming teams to gather items from the wreckage, and she was present to hear this. ("Pilot, Part 1") ("Pilot, Part 2") ("Tabula Rasa")
SBSSG by the signal fire.
She was also present for a portion of the day with Craig and the next day she with the group gathered wood for the mass funeral, and attended the funeral for crash victims. The next day she is seen with Jerome in the morning, and she, with the camp, saw a woman drowning in the sea, however they were unable to help her. At night when the group turns on Boone for stealing water, she was with Scott and listened to Jack make his "live together, die alone" speech. ("Walkabout") ("White Rabbit")
The next day she witnessed Jin deliver a beating to Michael seeing him wearing the Rolex Watch. After, Jack made a decision to move into the jungle and use the caves as a suitable living space, however she decides to stay on the beach. ("House of the Rising Sun")
When the tide shifted, she assisted the other survivors in salvaging the luggage which was floating into the ocean. That night, she joined her fellow camp in moving down the beach, and spent the night with Craig. A few days later, she was seen folding clothes with Richard. ("Whatever the Case May Be") ("Outlaws")
SBSSG attends Boone's funeral. ("The Greater Good")
She was present with the entire camp when Claire showed her newborn son to the camp. The next day she attended Boone's funeral and then witnessed the return of Locke who claimed responsibility for the accident, and was attacked by Jack. ("Do No Harm") ("The Greater Good")
When Danielle Rousseau arrived at the camp to deliver her dire warning about “the Others”, she was present to hear this, and later was witness to the black smoke that filled the sky, as she was helping the party with the raft. When Jack delivered his speech about gathering in the caves, she packed her supplies and prepared to leave. When the raft launched, she was present on the beach to say goodbye with her arm around Craig. ("Exodus, Part 1")
Days 46-55 (Season 2)
A few days later, the "Sexy Blue Striped Shirt Girl" walked along the beach and was present when Hurley passed out food from the Hatch. She also joined her fellow survivors on the beach to welcome the return of Jin, and the new additions of Bernard and Libby when they arrived after walking from the other side of the Island. ("Everybody Hates Hugo") ("Collision")
If she had not died prior to the beginning of time shifts, then she died in the flaming arrow attack in 1954, ("The Lie") since Rose and Bernard Nadler are presumed to be the only survivors of it. ("The Incident, Part 1")