Gertrude Middleton was Celeste Middleton's mother.
16 years ago, when Celeste was 12, she attended a sleepover. She was scared and called up her parents to pick her up. They became victims of car accident caused by Russell Wellington and her mom was in a coma ever since. Celeste used to visit her regularly and pay her medical bills.
Celeste, now going by the name "Charlie Bradbury", is once more in Kansas, to visit her mom and paid the brothers a visit. She was captured by a djinn and rendered comatose by a poison. In her subconscious, she fights off vampiric soldiers and in an endless loop, keeps saving her mom. Dean enters her subconscious via African Dreamroot and together they fend off the soldiers. She reveals that her mom used to read her The Hobbit every night before sleep. She was the one who got Charlie interested in the geeky stuff. Dean persuades her to let go of her fears. As soon as Charlie gives up saving her mom, she wakes up. The next day, Charlie bids goodbye to Sam and Dean who invite her to visit anytime and look through the Bunker's archives. Charlie has learned from her experience and decides to let her mother go. At the hospital, Charlie signs forms to have her mother taken off of life-support. But before she lets her mother die, she reads The Hobbit to her mother one last time.