Board Thread:Speculation House/@comment-70.195.206.131-20131110205644/@comment-3146930-20131110223548

Unless of course the Black Trailer was part of her training. She mentions that the White Fang only became aggressive about 5 years ago. Before that, Blake had no reason to learn how to fight outside of personal protection. Then she left the group and enrolled at Beacon. However she probably wasn't the only person in White Fang when they became violent so there are other members that are on the same level as Blake, or stronger.

However considering that the White Fang is known for attacks and robberies, Blake and Adam were probably just one team. I also don't think it would take as long as you think to replace her. Faunus in the series are mentioned as having natural skills that relate to stealth and infiltration. They have night vision, acute hearing, and possibly other improved senses (namely smell). If anything, the Faunus in general were made for stealth and infiltration, streamlining the process. Blake leaving was more of an inconvenience then a problem, otherwise they would have tried to get her back.