Jenda (formerly Jenda Simpson) is Bart's future girlfriend and eventual ex-wife.
Eight years into the future Jenda breaks up with Bart on a picnic date. In order to win her back Bart accepts an offer made by Mr. Burns to attend Yale on a scholarship, originally intended for Lisa. Jenda takes him back because he now has the scholarship and is "someone." Lisa, on the other hand, resigns herself to a life with Milhouse. Bart and Jenda take a walk and Jenda pressures Bart to have sex with her. Bart spots Professor Frink's house, remembering the astrology machine in the basement, and sees the dismal future Lisa has in store. Jenda is upset and demanding as she wanted to have sex with Bart and gives him an ultimatum: either Bart will take her now, or leave her to save Lisa's future. Bart is torn between staying with Jenda and saving Lisa, but chooses Lisa and sets off to save Lisa, giving her the scholarship. It also implied that Jenda had a relationship with Todd Flanders.
At some later point Jenda and Bart reconciled and married having two sons together. However, the marriage eventually failed. Thirty years into the future the two have divorced with Jenda evidently keeping custody of their children, though she tries to keep Bart involved as their father. Jenda now has a new partner called Jerry. 
(Useless trivia: Jenda is a less common colloquial form of the most common MALE name in Czech Republic - Jan.)