In the Star Wars Expanded Universe (EU) — which has been removed from the official Star Wars Saga canon timeline — after Star Wars Episode VI: Return of the Jedi there were stories where Han Solo and Princess Leia had children. Two of which were twins named Jacen and Jaina Solo. While the new retconned timeline has removed their EU stories from canon, it seems like Jaina could be making an appearance in Star Wars Episode VII.
According to the website MakingStarWars.net, they have alleged details about actor Daisy Ridley's look in Star Wars Episode VII. The website wrote:
"The details are very general but the costume gives the idea that this character might be more comfortable in a seedy spaceport than at a gala event.
"The artwork shows a slender brunette figure wearing clothing with a grey and brown palette. She wears a dark blue sash at the waist that hangs down at the back and one side at about thigh level. Her shirt arms have a few utilitarian looking straps attached and it covers both midriff and chest completely. She may wear gloves and have 'Star Wars' type wraps on the forearms.
"She wears a few pouches and belts.
"A lightsaber is clasped in her hand…"
While this is all RUMOR right now, with lots of speculation throughout this post, there are some similarities with this description and how Jaina has been portrayed in past Star Wars EU canon.
Star Wars Episode VII releases in theaters on December 18, 2015.