Why didn't Beatrice notice the witch's scent of Regulus? [spoiler discussion]

As far as I know Beatrice, like Rem, is able to smell/sense (it was never clear to me) the witch's scent, yet at this point when they meet Regulus she doesn't seem to be able to sense it (or if she does, it doesn't make sense that she wouldn't alert the others to it). Perhaps the reason is that Regulus, even though he is an archbishop of sin, does not possess such a scent? Is it part of his authority to be able to hide it?

As far as I know Beatrice, like Rem, is able to smell/sense (it was never clear to me) the witch's scent, yet at this point when they meet Regulus she doesn't seem to be able to sense it (or if she does, it doesn't make sense that she wouldn't alert the others to it). Perhaps the reason is that Regulus, even though he is an archbishop of sin, does not possess such a scent? Is it part of his authority to be able to hide it?