Muggles' Guide to Harry Potter/Characters/Eileen Snape

Overview
Eileen Snape (née Prince) was the mother of Severus Snape. She was a pure-blooded witch who married a Muggle man named Tobias Snape. It is said that she was the original owner of the advanced Potions book that her son and Harry Potter would later come to own. During her time as a student she was the captain of the Hogwarts gobstones team.

Order of the Phoenix
We first see Eileen briefly during Harry's occlumency lessons with Snape. We get a brief look into some of Severus's memories, in one of which we see a man shouting at a frightened looking woman while young Severus cries in the corner of the room. Though we don't learn their names, it is implied that these are Snape's parents.

Half-Blood Prince
We learn about Eileen at the end of the book. Hermione shows Harry and Ron some old Daily Prophet articles featuring an announcement that Eileen married the Muggle Tobias Snape, and one about how she had given birth to Severus. It is also stated that she was the original owner of Snape's potions book.

Deathly Hallows
We see Eileen very briefly in Snape's memories where she is accompanying her son to Platform Nine and Three Quarters.

Relationships with Other Characters
Based on what we see in Snape's memories, Eileen and Tobias didn't seem to have a happy marriage. Judging by the way she was cowering while he yelled at her, Tobias may have been abusive or at least highly unpleasant.

It's unknown how well she got along with her son, however he would later go on to use her maiden name to create his own nickname The Half-Blood Prince.

Analysis
Eileen was the original owner of the potions book which is described as being around fifty years old. Interestingly this places her at Hogwarts around the same time as Tom Riddle.