Like that ragefield guy, the nun keeps saying saintess but he acted as if he didn't hear it so it must have been 'My lady' instead cuz in this chapter when mc said she's saintess he was scared shitless.
And I think what she means when the priest finds out if she's not the real saintess it should actually translate to 'If he finds out I'm not the real Ariel, I'm dead' given that she possessed the og Ariel's body. My g** my reading skills after reading thousand bad translated books is already at peak HAHAHAHHA