Gwenyvere's parents were both taken from her at a young age. Shortly after she was born, her father died of the common cold (though many of his old friends suspect that he faked his death to become a food critic in Waterdeep). Her mother, when Gwen was only five, “went out for milk” and was arrested for prostitution.
This left Gwen a sad little orphan. She managed to survive on the streets for the next ten years due to her natural aptitude for stealing, and also looking just downright adorable. Luckily, Baldur's Gate is a fairly large city, with plenty of merchants to take pity on her and to be stolen from. She joined a gang of street urchins, which also helped her survive—especially during the winters. When she turned thirteen, she was given the task of actually picking pockets for the group – which helped keep the youngest urchins alive, as well as keeping everyone clothed. Honestly, she was quite lucky to become a part of this group of orphans, who were generally the most well-behaved of the street gangs.
When she was fifteen, things took a turn for the worse. The town guard cracked down on petty crime, and her gang was broken up. She managed to escape the priests and guards, but most of the other orphans were carted off to orphanages in a number of cities (wherever the churches had room, really). In any case, Gwen managed to keep her life on the streets for a few months before she pick pocketed the wrong person. His name was Henry Waterman (Human). He was an adventurer in his youth, and had retired from that to become a wealthy local—he owned a small mercantile trading ship which took non-perishable goods up and down the sword coast, he worked part time as a sergeant for Baldur's Gate's town guard, and he also worked occasionally as an ambassador to several smaller port cities in Calimshan. He caught her picking his pocket, and chastised her. Since she wasn't used to being verbally abused in lieu of physically abused when she was caught, she struck up a conversation with him, and later that night she was living in one of the spare bedrooms of his house. He adopted her the next week, and she enlisted in the town guard on her sixteenth birthday.
Over the course of the next fifteen years, a lot happened. For her military career, she finished basic training, and immediately was thrown into the kitchen. This was mostly because she was a very small woman, but because of all of her cooking experience with the orphans, she was able to make all of the meals taste not horrible! Over the years she got much better at cooking, but was never one for following orders. Because of this she was never sent on patrol outside of the city, but despite it she seldom reprimanded, possibly due to how persuasive she can be. Eventually she made it to the rank of Second Lieutenant, also known as Head Chef.
Her non-military life consisted of special training by her adoptive father. He taught her a little of everything he knew: how to be a merchant, how to be an ambassador, and how to survive in the wild. These were all very basic lessons, taught around basic etiquette and other household skills. She grew very fond of reading, and spent much of her free time waist deep in books. The rest of her free time she spent with Edgar, Henry's son. Henry's wife had died when Edgar was born, and Edgar was very pleased to have an older sister join the family. He was two years her junior, and also joined the town guard when he was old enough. They were close friends for quite a long time. Eventually, Gwen fell in love with her brother from another mother. This was very unwelcome by their father (and honestly, Edgar was too dense to even realize what was going on), who never broached the topic. Instead, when it went too far, he used his weight with the town guard to get Gwen sent on a sort of town guard exchange program. Now she's on her way to Greenest, where she'll be stationed for several months. She's looking forward to some time outside the city—she's never really left it. And Greenest sounds like an interesting enough place.