Sandra

"Hold your horses, Clem! Sorry. There's something in the treehouse, and she wants me to get a video of it to show you guys."

Sandra s an original character that appears in The Walking Dead Family Matters She is Clementine's babysitter. Clementine mentions her screaming a few days before Lee Everett and Clementine's uncle Jack Blake arrived at the house implying she was attacked by a walker, died and then reanimated.

Pre-Apocalypse
Not very much is known about Sandra's life. She was likely a paid babysitter for Clementine. She was asked by Clementine's parents, Diana and Ed, to look after their daughter while the two were on vacation in Savannah, but promised to be back before her spring break. During her parents' absence, and Sandra being her caretaker, the two discovered a raccoon up on the tree-house. Clementine asked Sandra to tape her interaction with it, as Clementine's parents call. In the conversation, Diana tells Clementine to be nice to Sandra, while Ed tells her not to get his hat dirty and that he let Clementine borrow it. After that conversation, Clementine says that she is looking forward to see both of her parents to come home

Post-Apocalypse
Before the outbreak, Clementine spots a raccoon in the tree house. Sandra comes rushing out of the door with a camera to video tape the raccoon. This raccoon is thought to be the same raccoon in Season 2, Episode 4.

A New Day Gone By

Sandra might have been hiding with Clementine in the treehouse for a few days before the former's untimely demise. At one point, Sandra left the treehouse to possibly seek help, use the phone or watch the news (which would explain why the television was on when Lee and Jack entered the house). It is implied that Sandra was attacked by a zombie two days before Lee Everett and Jack Blake arrived at Clementine's house. When Lee enters the house and looks around, he spots a pool of blood likely from Sandra and then hears Clementine on a walkie-talkie. When Lee slips in the pool of blood, Sandra crawls for him however she is shot in the head by Jack.

Death
Walkers (alive)

lementine says she heard Sandra screaming a few days before Lee Everett and Jack Blake

got to her house and then reanimated soon after. It can be implied that she was attacked by walkers. Lee Everett is attacked by Sandra and he struggles against her however she is then shot in the head by Clementines uncle Jack.
 * Clementine (Caused, Zombified)
 * Jack Blake (Zombified)

Travia
The scene where Sandra films the raccoon in Clementine's treehouse is only in the trailer for Don't Go Back.