She can’t see him in the mirror – she’s only sensing that he’s back there – so Integra hasn’t noticed the look just yet.
Integra: So…I’m getting younger.
At least these bloody expensive clothes still fit…
Alucard: They won’t for long.
Integra: Alucard, get out of the ladies’ room.
Alucard: Didn’t I say that form means nothing to me?