1 month ago:
Plot: Guy is a soldier at Winterfell, and Sansa's first crush. When Sansa is betrothed to Joffrey she is livid but as a proper lady she has to hide it.
She then notices Guy has an interest in one of her mothers maids and she becomes jealous; when she spies them together she steals some of the queen's property and pins it on the servant girl. When she informs the queen Cersei has the girl executed.
A year passes quietly enough without anyone suspecting Sansa of anything and she carries on pining after her father's right hand man. Then Guy takes an interest in another woman: Anne Boleyn. This time Sansa begins to lose control, even her maid starts to fear for her sanity.
When her moonblood starts, Sansa attempts to cover it up so she doesn't have to marry Joffrey, but it backfires. At the same time Guy and Anne get married. Sansa tries to garner Guy's attention more and more, making Anne suspicious and causing a rift between the couple. Guy tells Anne that Sansa's just a child, and that she's being ridiculous. Anne confides in her brother; which Sansa witnesses. She goes to the Queen claiming that she saw them together intimately. So, Anne and her brother are executed.
After this Sansa goes to Guy and confesses her love for him. He tells her that she is a child, and that he could never take advantage of Lord Eddard's daughter. He leaves her, questioning whether she had anything to do with her wife's death. Feeling rejected Sansa waits until Guy is asleep, and then stabs him to death. Her mid walks in and then helps get rid of the body and cover up the crime.