Jaina had a pretty typical childhood- kidnappings, attempted kidnappings, telekinesis, nannies, droid-nannies, Wookiee-nannies, hobos, Lightsabers, and high-stakes politics. Jaina developed strong mechanical skills, became a good pilot, and played around with the Force a little. She attended her uncle Luke Skywalker's Jedi Praxeum on Yavin IV, where she met other pre-teen Jedi, like Tenel Ka, and had some good old fashioned pre-teen adventures that taught her valuable lessons about life and friendship. Eventually, she became a Jedi Knight just in time for a big war.
When the Yuuzhan Vong showed up, Jaina was involved in several key battles and did a stint in Rogue Squadron, where she regularly showed up her fellow pilots. The war took Jaina all over the damned place. She continued to be trained in the Force by Mara Jade and Kyp Durron, had a traditional romantic comedy-style hate courtship with Jagged Fel, and even had her obligatory brush with the Dark Side after her little brother died. She did, however, figure out ways to mess with the Yuuzhan Vong, and pretended to be a goddess for a while. Apparently this was helpful, but she was much more comfortable raining down vengeance upon her enemies.
Other Big War
When the war ended, Jaina was eager to get involved in as much incidental combat as possible. Fortunately the Second Galactic Civil War kicked off, and Jaina had plenty of opportunities to bonk some heads. While she initially sided with her brother and the poorly named Galactic Federation of Free Alliances, she later followed her uncle in abandoning that side as Jacen continued his spiral into douchiness. Jaina decided that she was the only one who could take down her twin brother. In order to do this she trained under Boba Fett. Fett was a hard teacher who believed in a good balance of hard manual labor and humiliation, having learned how to train people from watching 80's movies. After the extended training montage, Jaina was ready to finish the job. And this time it was personal. They met, they dueled, she won.
Well, Did They or Didn’t They?
After that she got involved in some political stuff and may or may not have married Jagged Fel. If she did, she’s Roan Fel’s grandma. Probably.