Born in the last few years of the Thirty Years' War, Gwendolyn spent her early years in Murnord. She was, and still is, the apple of her parents' eye and doted upon by siblings and parents alike, though especially by her father, making up for his time away by giving her more attention than anyone else when he was home. At about age 9, she was sent off to a convent, in the southernmost parts of the l'Corren lands, not for "seminary" but simply for education.
She managed at the Convent for about three or four years, but her mischievous streak got the better of her and and the nuns. She was a brilliant mind even at a young age and became easily bored with basic lessons, finding her mind wandering to other things she could be doing. She did learn, at least, just faster than they could plan for, and was often assigned work scribing for the priests and nuns as both punishment and a means of keeping her busy. She wasn't mean to other students or anyone, really, but liked to go her own way, literally, sneaking out to the countryside around the convent on numerous occasions. Sometimes she hid in a cave, sometimes she simply walked until they found her but she always came back with an apron full of plants and rocks and other things to study. She did play the occasional prank as well that often times involved frogs or lizards, and eventually the Convent very politely asked the l'Corren to take her back.
Gwendolyn briefly returned home and as much as time matured her, so did the hint of disappointment in her father's eyes at her necessity of the convent to send her back. During her time in the Convent she had started to pick up a genuine interest in Healing and apothecary and expressed a desire to further her education and training in that field, promising better results and behavior. Given that around this time the battles with the Tirian Barbarians in the north that led to the First Siege of Valetta were heating up, the l'Corren saw the value in keeping her further south than Murnord, so they sent her to foster with the t'Resseaux, who are one of their southernmost vassal families and specialize in healing/training healers. She thrived with this new atmosphere and with this more focused training. She picked up on things quickly and was fortunate to have tutors who recognized it and made sure she was properly challenged.
After a few more years there, Gwen finally returned home to serve out an apprenticeship under the Master Healer of the l'Correns, blossoming in the role, finding her niche in helping and healing people. She also began what she considers her life's work, a healing manual of sorts, complete with pictures. Shortly thereafter, she met Joff and while their interactions were thoroughly proper, they basically become pen pals for a few months. Cesare caught wind of this, and decided it'd do the family good to have at least one family member wed into a vassal family, and Joff's reputation was as good as any, even if he was a lower ranking Noble. Gwendolyn and Joffrey get formerly betrothed right after Michael and Bella's Wedding. Shortly thereafter Joff went North to fight and Gwen stayed home with mom, continuing her training with the Master Healer. During his time away, Gwendolyn took advantage of the fact that her father did not tell her /not/ to sneak off and did just that, snuck to the front to see about Joffrey. Upon learning of her little stunt Cesare hauled them all up to the war camp to get Joffrey and Gwendolyn hitched.
After the honeymoon, Joff returned up North, and ended up being in the Second Siege of Valetta. Meanwhile, while Gwen was no doubt worried sick, she also had plenty to do, as plenty of wounded stragglers from the northern campaigns funneled down to Murnord for treatment. Plus she's been largely running the household while her Mom handles the day-to-day affairs of the Duchy while Cesare's away giving her plenty of experience with healing and stewardship.
When the final battles up north occur Gwen traveled with the camps and was in the healer's tents for Prince Jean-Paul's relief forces. She was able to be reunited with Joff right after the Battle was over.