The presence of a female guest in the castle became an unusual sight, but Leland had known Katherine from six years ago when she was hired to tutor Sophie to do bookkeeping, so he was not wary about her.
Back then, he already had Duncan investigate Katherine's background before she was hired. He knew Katherine was a lowly witch who loved studying human knowledge more than magic. She also helped Sophie a lot when she grew up in Hastings and taught her many things.
In addition to that, Katherine also seemed like a capable teacher. Katherine's presence helped Sophie a lot when she started living in Wolfstone Castle with Leland.
On the pretense that having Sophie work for Duke Romanov, seeing a familiar face there to teach her stuff and be her companion made Sophie's hard and lonely life after Nicholas' death become bearable.
