Karl came to the Souran territory with a mission and he soon needed to return back in order to make a report. His task was mainly to observe the situation and there was actually no need for him to make any moves here.
And now that he had became Weiss's subordinate, he needed to make sure that after hearing his report, both his Night Crow organisation and count Falgur would lose their interest in investigating the Souran territory even more.
But as Karl was not really very good at thinking about plans like that, he asked for Weiss's help in coming up with an idea. This was actually a good thing to do as making a half assed plan would just create more problems in the future. So asking for help was the right thing to do.
There was still some time left before Karl needed to return. So it was not like Weiss needed to come up with an idea right at this moment. So she decided to think about this matter a little bit more before finalizing any plans.
