As Megan, Jeff younger sister, passed by his room, she heard what sounded like some sort of electronic warning sound, the kind of thing you could expect to hear when some electronic apparatus wanted to alert you of some problem or other. Curious, she entered his room and saw a strange computer, a stranger retro-futuristic thing branded as a ‘TransDem Chronivac’. Its screen warned "Last change conflict with reality, please take corrective measure".
At first, Megan believed it to be some sort of retro video game on a customized machine (at least when it come to its look) but, after minimizing the error message and studying the software, understood it really was able to change reality. The amount of information that thing got on her was damn' scary!
Going back to the warning message, she choose the "more details" option and saw the problem was her mom being a teenager again while still being the family's mother. Thinking it was Jeff's idea of an early birthday gift for their mom, who often complained about all the little pains her body gave her in her older age, sometime going so far as whispering, "If only I was a teenager again!" decided to think on a way to remove the conflict without changing their current family dynamic.
As such, she got into the advanced option and entered that Sherry had somehow stumbled onto a way to get younger, unaware. So unaware, in fact, that she can't figure how she turned back into a teenager, just that she did. Then she needed to prove she was who she claimed to be, having somehow gotten younger, which was an administrative nightmare. But said administration had ultimately relented, finally admitting that she really was Sherry, mother of Megan and Jeff.
Thanks to that, she had regained all her diplomas (driving license include), got a new job after her age-regression cost her the previous one, and even regained her marital status with her husband. Unknown to Megan, that last one wasn't without its problem. Not that Sherry loved her husband any less since being a teenager again, but it didn't change the fact that, now being the same age as Jeff, the love of her life was old enough to be her father. (If only she could remember how she rejuvenated…)
Not only that, but the mother was also going through puberty again, which wasn't without its lot of mental effects. While Sherry still was the loving mother her kids knew, since becoming younger she could act as your typical teenager, at times.