Leah is mentioned by name in the gameplay trailer. The barbarian says to Deckard Cain that Leah worries for him. (Leah was confirmed as her name when Blizzard called her that in an official wallpaper.) It seems that Leah gave the player the quest to rescue Deckard Cain in the catacombs below the old Tristram Monastery.
There is an interesting passage in the Gnarled Walkers lore entry in the official page, concerning the village of Wortham:
- "I likewise found it odd that there seemed to be only elderly people in the village, with the exception of one beautiful young woman whose father was quite insistent I keep my distance from her. Though he was rude on this point, I found him to be a rather sociable sort once convinced I was not interested in his daughter. He introduced himself as Pablo DeSoto"
There is speculation going about that Leah, the girl from the cinematic trailer, is actually the daughter of Pablo DeSoto mentioned in the lore. Other speculations include Leah being the new narrator, Cain's daughter or apprentice.
Be as it may, it is clear that there is some significance to the appearance on the cinematic trailer, as these take a substantial amount of time to prepare. Any random NPCs may be dropped out of the game as the development progresses but Leah was important enough to be put in the trailer which they had to begin working on months before the game announcement.