(If this question is in another thread please point me there.)
In Blood Rites, why was Mavra's crew in place at Arturo Genosa's when Harry and Thomas drove up to the outer guard shack? Its clear Mavra decided to draw Harry into attacking her so she could later blackmail him to get the word of Kemmler for her.
How could she have possibly have known Harry would show up there?
My personal theory is that she and the White King, as part of the Black Council, were working together. Both Mavra being there with vamps at the guard shack as well as Madge, an ex-wife whom purposefully avoids making contact with Harry, indicate Papa Raith knew someone might interfere and that it might be Harry. Blood Rites was the White King's attempt to break free from Maggie's death curse.
Just as we had seen Cowl and Kumori at Bianca's ceremony, it was also implied if not outright stated that Mavra was Bianca's teacher in the magical arts. We find out later that Maggie Sr. was with the White King and wanted Eb's help with some plan and that Duchess Arianna was there as well.
This strongly implies that the White King was BC and that Arianna was as well. If we tie in Mavra to the scheme, we have a link between these factions. Mavra, I think, was there in part to gather new henchmen but also to prevent any interference to the White King's plans to bring Genosa 'back into the fold'. Someone like Harry would be such an interference.
Since she 'failed' and the White King fell in that book, it also keeps in line with Harry's later musings that the Black Council plays all nice with each other until it is time to stick the knife in one of their fellow council members' backs.
Net results of Blood Rites for the bad guys: Mavra gets blackmail material she later uses to get the word as well as deposing a fellow Council member. Black Council removes a member that may have been to locked into out-moded thought processes. Oh, and I think they gain a new Council member: Lara.
Whom better to join a group of self-serving, backstabbing, work-behind-the-scenes-to-destroy-everyone-else club than Lara Raith? After all, she now has access to all of Papa Raith's knowledge. I don't think Lara is one to just sit on information, such as it were.