I saw it through his blood memories. He didn't expand upon much beyond what I witnessed.
[So many questions, though. She's not sure where's a good spot to begin.]
Both Kaname and that woman were involved with each other's efforts from the start. Kaname realized early on that the only way to injure a pureblood was likely by the power of another pureblood. With that information in mind, he realized the most effective method, but - she did it before he could.
As for why... [She shakes her head, eyes lifting to glance back up at him. Is it that difficult to understand? Putting aside whatever has changed in the present...] That women...didn't hate humans. Neither did he.