Yep, Seth did - the others are a bit more in denial! I think Jessamy is still young enough to believe grown ups can sortjust about everything and to find all the stories real - especially with the "proof" of Edwin's state that she is more reassured than freaked out by Willem. She accepts him as a wizard whether he is or not - and really Bree must have been such a limited place that he would seem magical to her even if he didn't have furry pyjamas ..
And she knows and trusts Karl and he has vouched for Willem...
So not annoying at all.