I'm not sure what kind of constructive criticism you're talking about, like if it's about the oc's appearance or their biography, but I'll talk about their appearance, it doesn't look bad but you could have chosen softer colors to match with the light yellow(I'm referring to the shade of blue used in the outlines, they're too dark for me), the knife could be a little redder too, cause looking at it like this it just looks like she's holding a knife, not that she's an imposter, maybe you could've give the eyes a red shine effect to make it more obvious that she's an imposter, aside from all that the only thing I don't like is the black eyebrows and black mouth as it doesn't match with everything else on the character, overall I'd give it a 6/10
Don't take this too seriously though that was just my opinion it's nothing you should care about :P