Well momoko, she's the strongest after all! why would it be bleeding or anything for something as puny as being stabbed? it's not like she's like one of those puny and weak average yukkuris, she's the strongest!
@Mokomoko What JIE said, and also the fact that Cirnos are supposed to have ice-cream as filling, which wouldn't really 'bleed' much unless it was melting.....