The question that most people would wonder is why did Lirian make it seem like Lady Liberia was responsible for the death when he wanted to bring damage to House Kurt.
The answer was simple, it was to create an element of chaos amongst the nobles.
If the nobles believed that it was House Kurt, there wasn't much that they could do aside from feeling frustrated.
House Kurt was the dominant power, even if the minor nobles believed whole heartedly that it was House Kurt who killed Lord Grant, no one would be able to do anything.
The minor nobles were bound to feel too afraid to act up, for fear of Lord Ventrano's death repeating itself, only this time it would be them and not Lord Ventrano to die.
It was for that reason that Lirian introduced an element of chaos.
When Lirian entered Lord Grant's study in the night he let Lord Grant see his reflection in the window for a second to get Lord Grant to think about him.