Jenna Duffy a.k.a. the carpenter is from DC comics and Batman she used to be a villain if you use that term very loosely.
She was actually on the planet for a long time before she showed up on Harley's doorstep. Nobody knew who she was and she couldn't muster the confidence to identify herself as an aspiring villain.
Much to the surprise of Batman and the girls Police Chief Elisa Maza dropped her off at their house after the festivities of Christmas morning were up. Batman immediately got the idea to use her skills in deathtrap making to make fake deathtraps for children who want to be heroes.