Jenny is a student at Gunnerkrigg Court. It is unknown which house she is in, but it is likely Queslett or Chester as she's a sorcerer apprentice. She is also in a relationship with Jack. She also bears a bit of a similarity to Zimmy
She came to the court presumably to learn to make wards and other spells.
At some point after the end of year 8 she got to know Jack and asked him out, it is not known if she knew about his feelings for Zimmy at the time, but by the time she's first seen in Chapter 49: The Torn Sea she knows all about it. Jack even says she helped him through a few things.
By the end of year 9 she goes on the Cruisebot with Jack as her date. When Jack notices that Zimmy is on the boat the two go away to try contact the coast by radio, when that fails, Jack builds a small airship and Jenny makes a seeking ward to guide the ship.
When the ship is warped into Zimmyngham she shows fascination and endorsement for the place. She then tries to use a spell on the tome on Annie's arm to deactivate it, but is unsuccessful.
Later, when the students have located Zimmy, Jenny put on Zimmy's clothes and takes her place to distract the Seraphs while the rest of the students are getting away. When the Seraphs are right where she wants them she stomps on the middle circle of a three-part ward, the third which is located under the seraphs then emmits some sort of energy strike.
When all the fighting is over she later reunites with Jack.