Okay, I do not think it is possible for Lady Jane Grey to be Queen Regnant, but if you want her Queen, she'd have to wed Edward on his 14th birthday (which, according to everything I'm finding, was about her 14th birthday as well) and have a child. If the child is a girl, Edward might be able (with the help of those who wanted Protestant reign continued) to establish a regency council - but England likes neither female nor minority rule. Civil War city.
If she has a boy, however.......but that's still a long time Regency Council on top of one for Edward and the monarchy is liable to falter big-time, losing a lot of power to a "advising council" that would be 20 years in place.....(estimate)
There is no joy in a Queen Jane. Just a long haul.