A trader who came from Barclay to acquire Noldor artifacts, or barring that, simply make a profit on a trade route between Laria and Javiksholm. She and her brother were ambushed by the Jatu and despite putting up as best a fight as they could, their guards and her brother were killed. She is gentle, and does not like all the blood and killing, but accepts it as part of being in a mercenary troop.
Since she is a merchant by trade and was originally just looking for work as a quartermaster due to losing anything she could have used to restart her merchant career to the Jatu, when she joins she only has a set of throwing knives, ankle boots, a blue dress, and a knife, but like Ansen she has the potential to become a very strong warrior in her own right given enough time.
She likes Diev, who keeps Kassim from bullying her and find her as very inspiring due to the mess she went through and the family she lost. She also hates Donavan for his cruel methods and his frequent threats to flog her.
She will hire on with you for free.
Leslie, along with Ansen, is the most versatile and useful companion in the game. Given that she's at level 1 when hired, you can build her any way you see fit. However, the most useful build for her is fairly simple: up her STR just enough to have her equip some halfway decent armor, give her a basic shield, sidearm, and the Arquebus and Bullets for weapons, and then go whole-hog into upping her INT. Leslie can serve any INT-based role for the party: make her the medic with healing abilities, or the pathfinder with scouting skills, plus making her the party's Engineer. Given enough time, she could conceivably fill ALL THREE of those roles.
She is a commoner, making her a lord will result in her recruiting the original culture troop type of whatever fielf you give her villiage or castle. (3.9.5)