haven't seen anyone mention frieren says she's used to her master begging , that statement is given crazy context in the future , in terms of just what kind of begging
Being a first class mage is not a right,
They're direct student's /subordinates who take instruction / missions from Serie, which Frieren has no intention of doing
that makes no narrative sense,
she already detected he was a warrior and
they had a battle with the last person who she detected as a warrior and they're in capital expecting an assassination and will encounter a group....