You learn that there's a local who has some vast store of knowledge. Despite him being ostensibly aligned with Stormwind and so theoretically against your superiors, it's easy to convince him to attend a dinner for some important occasion or other. It requires practically no effort from you to get him to start talking at said dinner. "...and then," he explains after about half an hour, "there was the deplorable death of the Queen. We think she was killed by none other than the well-known Defias infiltrator, Dewayne Gold! But that is a matter of debate. At any rate, it led all the Stonemasons, including Edwin VanCleef and his daughter, whose mother must have been killed earlier too—also deplorable—to be kicked out of Stormwind City and become...the Defias Brotherhood." He pauses for effect. "And then I hear they killed this couple called the Furlbrows recently," he adds as an afterthought. "I think one of them used to be a Stonemason too? Defias must have wanted any witnesses killed off." "Excuse me," says a voice from the other end of the room. "What is going on here?" You see the shadowy figure you work for enter the room. She isn't paying any attention to anyone else here, including the orator. Just you.
Claim that you're uninvolved in this. Use the story and any support you may have gained to turn the gathering against Vanessa. Feign unawareness of what's going on.